A – Wrong
Having a gravity similar to Earth is not a sufficient enough condition for supporting life.
B – Wrong
Liquid water being able to form oceans, lakes and rivers is not a sufficient enough condition for supporting life.
C – Correct
This is correct because of the line “planets like this must be really common”.
D – Wrong
“is probably in the order of 10 or 20 per cent” is different from “10 or 20 per cent of systems have“.
This statement is too strong.
E – Wrong
The text says that “there could be” and not “there are”. One word makes the whole difference. This statement is too strong.