A meteor is:

Answer: (b) a piece of mater which has entered the earth's atmosphere from outer space

A meteor is matter from space entering Earth’s atmosphere and burning up.

The idea

A meteor is the brief light phenomenon caused when a small space body enters the atmosphere at high speed. Compression of air and interactions with the incoming body generate heat and light. The visible streak is different from the object before entry or its surviving remains.

Earth meets a small space fragment → Fragment enters the atmosphere at high speed → Air is compressed and the body heats → Material is lost and a luminous streak appears → The body disappears or a remnant reaches the ground

Why the others are wrong

(a) Meteors aren’t stars (“shooting star” is a nickname).

(d) A comet has a nucleus and orbit; it is not a meteor.

The trap

“Shooting star” suggests (a).

Also know

Meteor showers occur when Earth crosses a stream of debris, often left by a comet. The shower’s radiant is the point from which the streaks seem to spread. A meteorite can be stony, iron-rich or a mixture of stone and metal; a crater forms only when an impact has enough energy.