Answer:
(a) No; rainfall amounts are positive
Explanation:
Rainfall amounts are measured using a gauge that reports the amount as zero when the gauge is empty. Any rainfall adds to the amount in the gauge, so is reported as a positive number. There is no way to remove more rainfall than is in the gauge, so there is no way to have a negative rainfall amount
A prediction of a negative rainfall amount makes no sense, because you can't have a negative amount of rainfall.