Answer:
The correct answer will be A. map.
Explanation:
Technically, neither answer is correct. Given that the subject of the sentence is the plural noun phrase <em>storm trackers, </em>that would mean that the verb also has to be plural, and neither one of those two options are. Both verbs are singular: <em>maps </em>and <em>is mapping, </em>and they should be plural: <em>map </em>and <em>are mapping.</em>
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 <em>track, </em>which is present simple, which means that the second verb should also be present simple <em>map. </em>Also, given that this is something that storm trackers do usually, it is safe to assume present simple <em>map </em>is the correct answer.