BIOLOGY
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چار آپشن میں سے کسی ایک پر کلک کرنے سے جواب سرخ ہو جائے گا۔
سائیکل چلنے کی حالت میں مستحکم کیوں رہتی ہے لیکن کھڑی ہونے پر آسانی سے گر جاتی ہے؟
- Friction increases at higher
- Gyroscopic effect of rotating wheels
- Air resistance stabilizes motion
- None of these
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Explanation
- A bicycle stays stable in motion due to the gyroscopic effect of rotating wheels, which resists tilting.
- When the wheels spin, they create angular momentum that keeps the bicycle balanced.
- At rest, there is no rotation, so no gyroscopic stability is produced.
Last verified on 14-06-2026
ذیابیطس میلیٹس میں بار بار پیشاب آنے کی کیا وجہ ہے؟
- Glucose reduces ADH secretion
- Insulin increases water excretion
- Glucose increases osmotic pressure in renal tubules
- None of these
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Explanation
- Diabetes mellitus causes polyuria because glucose increases osmotic pressure in renal tubules, pulling more water into urine.
- High blood sugar exceeds the renal threshold (~180 mg/dL), so glucose appears in urine (glycosuria).
- This extra glucose draws water with it, increasing urine volume (osmotic diuresis).
- Normal blood glucose is about 90–100 mg/dL (fasting).
Last verified on 14-06-2026
ورزش کے دوران دل کی دھڑکن کیوں بڑھ جاتی ہے؟
- Increased vagal stimulation
- Decreased oxygen demand
- Increased sympathetic stimulation releasing norepinephrine
- None of these
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Explanation
- Heart rate increases during exercise due to increased sympathetic nervous system activity releasing norepinephrine.
- This prepares the body for higher oxygen and energy demand.
- It increases heart pumping strength and speed.
- More blood reaches muscles for ATP production.
- This is a normal physiological response during physical activity.
Last verified on 14-06-2026
جگر کے خلیوں میں ادویات کو زہریلے اثرات سے پاک کرنے میں سب سے زیادہ کون سا عضو حصہ لیتا ہے؟
- Smooth endoplasmic reticulum
- Lysosome
- Mitochondria
- None of these
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Explanation
- The smooth endoplasmic reticulum (SER) is responsible for drug detoxification in liver cells.
- It contains enzymes that break down harmful drugs and toxins.
- This process makes substances less toxic and easier to excrete.
- Liver cells have abundant SER for this function.
Last verified on 14-06-2026
الکحل اعصابی نظام کو سست کرنے والا مادہ کیوں ہے؟
- It accelerates nerve conduction
- It blocks dopamine receptors
- It enhances GABA activity
- None of these
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Explanation
- Alcohol acts as a depressant because it enhances GABA activity in the brain, which slows nerve signals.
- GABA is an inhibitory neurotransmitter that reduces brain activity.
- This leads to relaxation, slower reactions, and reduced coordination.
- Alcohol also suppresses excitatory signals.
- That is why it causes drowsiness and impaired judgment.
Last verified on 14-06-2026
سرخ خون کے خلیوں میں نیوکلیس کیوں نہیں ہوتا؟
- To maximize space for hemoglobin
- To reduce oxygen consumption
- To increase lifespan
- None of these
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Explanation
- Red blood cells lack a nucleus to maximize space for hemoglobin, which carries oxygen.
- More hemoglobin means more oxygen transport.
- This makes RBCs highly efficient for gas exchange.
- Lack of nucleus also gives them a flexible shape.
- This helps them pass through narrow blood capillaries.
Last verified on 14-06-2026
معدہ ہائیڈروکلورک ایسڈ کیوں خارج کرتا ہے؟
- To absorb glucose
- To dissolve fats
- To activate pepsinogen into pepsin
- None of these
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Explanation
- The stomach secretes hydrochloric acid (HCl) to activate pepsinogen into pepsin for protein digestion.
- HCl creates an acidic environment in the stomach.
- This acidity helps enzymes work properly.
- It also kills harmful microbes in food.
- Thus, it supports digestion and protection.
Last verified on 14-06-2026
کم وقت میں بہت زیادہ پانی پینے سے نقصان کیوں ہوتا ہے؟
- Water increases blood viscosity
- Kidneys stop filtering water
- Excess water dilutes sodium levels in blood
- None of these
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Explanation
- Drinking too much water quickly causes harm because it dilutes sodium levels in the blood (hyponatremia).
- Low sodium disrupts normal nerve and muscle function.
- Cells may swell due to water imbalance.
- This can affect brain function and become dangerous.
Last verified on 14-06-2026
شدید ورزش کے دوران پٹھوں میں لیکٹک ایسڈ کیوں جمع ہوتا ہے؟
- Carbon dioxide accumulates excessively
- Oxygen supply is insufficient for aerobic respiration
- Muscle fibers break down proteins
- None of these
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Explanation
- Lactic acid builds up in muscles because oxygen supply becomes insufficient during intense exercise.
- Muscles switch to anaerobic respiration for quick energy.
- This produces lactic acid as a by-product.
- Accumulation causes muscle fatigue and burning sensation.
- It is a temporary process until oxygen levels recover.
Last verified on 14-06-2026
ٹھنڈا پانی عام طور پر گرم پانی کے مقابلے میں پیاس کیوں بہتر بجھاتا ہے؟
- Cold water reduces oral temperature, stimulating nerve endings
- Cold water contracts stomach muscles, speeding absorption
- Cold water dissolves salts faster in the bloodstream
- None of these
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Explanation
- Cold water quenches thirst better because it reduces mouth temperature and stimulates nerve endings, giving a stronger refreshing feeling.
- This signals the brain that hydration is occurring.
- The cooling effect provides immediate relief from dryness.
- Warm water does not create this strong sensory response.
- That is why cold water feels more satisfying when thirsty.
Last verified on 14-06-2026
