The correct answer is: will be.
The sentence “If it rains the match will be cancelled” is in the future tense. It is a conditional sentence, which means that the second clause (the consequence) is dependent on the first clause (the condition). In this case, the condition is “if it rains” and the consequence is “the match will be cancelled”.
The verb “to be” is used in the future tense to talk about things that are going to happen. In this case, the match is going to be cancelled because it is raining.
The other options are incorrect because they do not agree with the tense of the sentence. Option A, “be”, is in the present tense. Option B, “will be”, is in the future tense, but it is not the correct form of the verb “to be”. Option C, “will”, is in the future tense, but it is not the correct form of the verb “to be”. Option D, “will have been”, is in the past perfect tense, which is not the correct tense for this sentence.
In conclusion, the correct answer is: will be.