![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
All of the following statements about the tails of comets are true EXCEPT:
A.
They can contain electricaily charged or neutral particles.
B.
They can be formed only when there is sufficient heat.
C.
They are formed before the coma expands.
D.
They always point in the direction away from the Sun.