Gerald and his family are at point A when they receive an alert that a

Gerald and his family are at point A when they receive an alert that a cloud of poisonous gas is moving toward them from the southwest. They need to avoid the cloud of gas by driving to a shelter at point B. If they must stay on the grid and are only able to drive north and east, how many different routes can they take from point A to point B?

A. 12
B. 15
C. 21
D. 30
E. 35