Answer
They are mutually exclusive.
Work Step by Step
The events “1-2 activities” and “3-4 activities” have no outcomes in common.
So:
N(1-2 activities and 3-4 activities) = 0
Or:
$P(1-2~activities~and~3-4~activities)= \frac{0}{N(S)}=0.$
They are mutually exclusive.