On leave - on strike?

[Kai]

Test No. incompl/inter-1 "Applying for that Job", question 4

The reason there are no buses is because the drivers are on ..........

(a) hit
(b) stop
(c) strike
(d) leave

Test No. incompl/inter-1 "Applying for that Job", answer 4

The reason there are no buses is because the drivers are on strike.

Correct answer: (c) strike
_________________________

Why can not use leave ?

[Torsten]

If you are on leave you are on vacation; you want to relax from work.
If you are on strike you refuse to work (you are not working) because you want to achieve better working conditions.

TOEIC listening, talks: Advertising a detox program