Answer:
The correct answer will be A. map.
Step-by-step explanation:
Technically, neither answer is correct. Given that the subject of the sentence is the plural noun phrase storm trackers, that would mean that the verb also has to be plural, and neither one of those two options are. Both verbs are singular: maps and is mapping, and they should be plural: map and are mapping.
However, in order to keep parallelism in the sentence, the second verb should have the same tense as the first verb. The first verb in the sentence is track, which is present simple, which means that the second verb should also be present simple map. Also, given that this is something that storm trackers do usually, it is safe to assume present simple map is the correct answer.