Explanation

T cells are responsible for recognizing and attacking infected cells, particularly those harboring viruses or intracellular bacteria.

B cells primarily target invaders outside of cells by producing antibodies to neutralize pathogens.

Explanation

During lightning or electrical discharges, nitrogen (N₂) reacts with oxygen (O₂) to form nitric oxide (NO).

This is the first step in the natural nitrogen cycle involving atmospheric fixation.

Explanation

Natural disasters such as earthquakes, volcanic eruptions, and floods can alter the Earth's surface, changing the shape of the land.

These events can lead to the formation of new landforms or the destruction of existing ones.

Explanation

When the left ventricle contracts, it pumps oxygenated blood into the aorta.

This blood is then distributed to the entire body through systemic circulation.

Explanation

Motor neurons carry impulses away from the central nervous system to effectors like muscles or glands.

They are responsible for triggering responses such as muscle movement.

Explanation

The sclera is the tough, white outer layer of the eye that provides protection and structure.

It surrounds most of the eyeball, except for the cornea at the front.

Explanation

Explanation

Dolomite is a carbonate mineral composed of CaMg(CO₃)₂.

It contains both calcium and magnesium carbonates, making it a double carbonate salt.

Explanation

Tetanus toxin (produced by Clostridium tetani) affects the nervous system, blocking inhibitory signals to muscles.

This causes sustained and painful muscle contractions.

It is also known as "lockjaw" or spastic paralysis.

Explanation

In 1827, Robert Brown observed the random movement of pollen grains suspended in water under a microscope.

This phenomenon was later termed Brownian motion, describing the erratic motion of particles in a fluid.