Explanation

 The brave do not yield to the enemy.

بہادر دشمن کے سامنے نہیں جھکتے۔

"Yield to" is a common phrase meaning to surrender or give in to someone or something.

In this sentence, it means the brave do not surrender to the enemy.

Explanation

اس کی بیماری اسے بستر تک محدود کر دیتی ہے۔

Explanation

"He is vain of his beauty."

The correct preposition to use with "vain" (meaning overly proud) is "of."

"Vain of" means proud of (in a conceited way).

Explanation

The phrase "hit someone on something"

Indicates that the action of hitting is directed at a specific part of the body or object.

In this case, "the bad touch" is considered as the target of the hitting action.

"On" is the preposition that denotes contact with something. 

Explanation

 You must comply with the teacher’s advice.

آپ کو استاد کے مشورے پر عمل کرنا چاہیے۔

The correct preposition after "comply" is "with".

 It's used in contexts where you are required to abide by a rule, instruction, or request.