As a vector for the introduction of nonnative species, why is hull fouling particularly difficult to combat?

It is difficult to combat because hull fouling is unintentional

Explanation:

Since hull fouling is unintentional deposits on non-native species into an environment, meaning it is accidental and one may not necessarily know they are introducing a non-native species.  The term comes from when originally non-native species were introduced unintentional, unknowingly and accidentally by attaching themselves to the hulls of ships in one ecosystem where they are native, then traveling and being deposited/inroduced, unintentionally and unknowingly, into the new ecosystem where the species is not native.  Since the non-native species is introduced unintentionally, accidentally and often unknowingly, makes it difficult to detect and control the non-native species, making it particularly difficult and hard to combat and or prevent.

the answer is b: 1.4 km/hr

the answers are a and c