Question

what does the idiom in this text mean?
in september 2013, president obama stated that he was on the fence about ordering a military strike against syria.
the president was firmly against the military strike.
the president was undecided about the military strike.
the president was enthusiastic about the military strike.

Explanation:

The text says President Obama was "on the fence" about ordering a military strike against Syria. "On the fence" means undecided. The first option says he was against it (contradicts "on the fence"), the third says he was enthusiastic (also contradicts), so the second option matches.

Answer:

The president was undecided about the military strike.