Answer:
D. Polaris and Sirius are farther away than the Sun.
Step-by-step explanation:
The radiation intercepted by Earth is inversely proportional to the square of the distance from the source. Polaris and Sirius are substantially farther away than the sun.
Polaris, for example, is about 27 million times farther away, so even though it is 4000 times brighter, we receive on the order of 5×10^-12 as much radiation from that star as from the sun.
We feel less heat from stars other than the Sun because they are farther away.