Answer:
Why is the match postponed?
Explanation:
A statement is a full sentence that presents or tells us about something. And in order to change the statement into a question, specifically the "wh" question, there is the need to start the question with "who, what, where, whom, why" etc., and also the use of the question mark "?" at the end.
The given statement "the match is postponed because of the rain" presents a case where a reason is an answer for the possible "why" situation. And in changing the sentence into a "why" question, the question will be "Why was the match postponed?"
