Why does this route fail to appear in the IP routing table?

Refer to the exhibit.

The network administrator enters this command:

Switch(config)# ip route 172.16.2.0/30 192.168.1.100 metric 1 distance 1

Why does this route fail to appear in the IP routing table?
A . Its prefix length is invalid.
B . Its next hop is unreachable.
C . Its administrative distance is the same as an existing static route.
D . Its metric is the same as an existing static route.

Answer: B