What is the reason behind the tail of a comet moving away from the Sun?
A The gravity of Jupiter pulls it away from the Sun.
The nucleus of the comet propels it away from the Sun.
C. The radiation pressure and solar wind propels it away from the Sun.
B.
D.
No valid hypothesis has been made yet.

The nucleus of the comet propels it away

Hello There. A The gravity of jupiter pulls it away from the Sun.

The streams of dust and gas thus released form a huge, extremely tenuous atmosphere around the comet called the coma, and the force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun.

i think the answer is a, hope this is right, that would be my best guess.