Explanation

Antibodies are proteins produced by the immune system to neutralize or destroy antigens (disease-causing agents).

They are a key part of the body’s defense mechanism against pathogens like bacteria and viruses.

Explanation

It is a question that asks if something happened — a key sign of an interrogative sentence.

It starts with "Did", a common auxiliary used to form questions.

Explanation

The phrase should be "used to" (with "d"), as it refers to a past habitual action.

"Use to" is incorrect after "was" — past tense requires "used to."

Correct sentence: When I was a child, my father used to take care of me.

Explanation

5% of 16,000 = 800, so increase = 800.

New population = 16,000 + 800 = 16,800.

A percentage increase means adding the calculated percent value to the original number.

Explanation

Explanation

Explanation

Melting of ice changes only the state from solid to liquid.

No new substance is formed, so it's a physical and reversible change.

Explanation

Explanation

The graph of x = a is a vertical line.

It is perpendicular to the y-axis, which is vertical.

Explanation

Supplementary angles add up to 180 degrees but aren't necessarily equal.

Supplementary angles can have various measures (e.g., 90° + 90°, 120° + 60°, 150° + 30°), showing they don't have to be equal.