Explanation

The cerebrum is the largest and most developed part of the brain.

It is responsible for thinking, memory, and decision-making.

Humans have the largest cerebrum relative to body size, enabling advanced cognitive functions.

Explanation

A zygote is the first cell formed when a sperm fertilizes an egg.

All the trillions of cells in the adult human body arise through mitotic divisions from this single zygote.

Explanation

Crossing over occurs during meiosis, where genetic material is exchanged between homologous chromosomes.

This process produces recombinant chromatids, which carry a new combination of genes.

Explanation

In polio, approximately 1 out of every 200 infections leads to irreversible paralysis, often in the legs.

Though most infections are mild or asymptomatic, this small percentage represents the severe impact of the disease.

Explanation

Ancient Greek medicine believed that health depended on the balance of four bodily fluids or "humors": blood, phlegm, black bile, and yellow bile.

Imbalance in these humors was thought to cause disease.