According to Hume, Why Can't We Have Knowledge on the Relation

Multiple Choice

According to Hume, why can't we have knowledge on the relation of cause and effect?

A) We can never observe a constant conjunction between events.
B) We can never observe the cause and the effect at the same time.
C) We can never observe a necessary connection between events.
D) We can never observe the atoms that make up the cause and the effect of events.