Equal amounts of heat are added to equal masses of substances A and B at the same temperature, but substance B gets hotter. What is true of their heat capacities (c)?

The one with the lower specific heat.
Explanation:
A substance's specific heat tells you how much heat must be added to / removed from a
1-g
sample of this substance in order to get its temperature to change by
1
∘
C
.
When energy in the form of heat is absorbed, a substance's specific heat tells you exactl;y how much heat is needed in order to increase the temperature of
1 g
of this substance by
1
∘
C
.
This means that the higher the specific heat of a substance, the more heat will be needed in order to get the temperature of
1 g
to increase by
1
∘
C
.
In your case, two substances, let's say
A
and
B
, start at the temperature,
200
∘
C
and they both absorb
150 J
of heat. Moreover, they both have the same mass.
If the specific heat of
A
is higher than the specific heat of
B
, you can say that it will take more energy to raise the temperature of
A
by
1
∘
C
than to raise the temperature of
B
by
1
∘
C
.
So, if
B
absorbs
150 J
and gets to a final temperature
T
B
, the fact that
A
has a higher specific heat will tell you that absorbing
150 J
of heat will not get the final temperature of
A
,
T
A
, to the same value as
T
B
.
You can thus say that
T
A
<
T
B
The substance with the lower specific heat will heat up more than the substance with the higher specific heat.

The answer is d.potassium