Why, According to Hume, Do People Suppose There Is Necessity

Why, according to Hume, do people suppose there is necessity between cause and effect but not between motive and action?

A) Because our observation of cause and effect is different from our observation of human action
B) Because their natures are fundamentally different
C) Because when they turn to the operation of their own minds, they feel no such connection
D) None of the above