Question

The number of pedestrian subways in the City (has/have) almost doubled. Give Reasons For The Answer

Answer 1

The number of pedestrian subways in the city have almost doubled.

Here, the subject is in plural that is pedestrian subways.
So "have" is the correct answer as it is used for plural subject

Answer 2

The number of pedestrian subways in the city has almost doubled.
Has is the correct answer because in the starting it's the number of ...when it is the number of we use singular verbs and when it is a number of we use plural verbs.


Hope it helps!