She could not come because of the heavy rain.

The correct answer is Option (1) → Adverb of Reason

An adverb is a word that tells how, when, where or how much something happens. It can also describe an adjective or another adverb, for example she sings sweetly, very hot.

Here, “because of the heavy rain” tells why she could not come.

Option	What it tells	Example
(1) Adverb of Reason (answer)	why something happens: phrases with “because of” or “owing to” often do this	The match was stopped because of bad light.
(2) Adverb of Time	when something happens (today, yesterday, at night)	We will leave for Jaipur tomorrow.
(3) Adverb of Place	where something happens (here, outside, at home)	The children are playing outside.
(4) Adverb of Manner	how something is done (slowly, carefully)	Please write your answers neatly.