Answer: a.
and
.
Explanation:
Let p represent the proportion of all households in the city that gave a charitable donation in the past year.
Reseracher wants to check whether p > 50% or p > 0.5
Since Alternative hypothesis contains ">, <, ≠" and null hypothesis is the opposite of alternative hypothesis.
So Null hypothesis:

Alternative hypothesis:

The correct option is a.
and
.