Oh? Which of the two are we going to have easier time explaining to the pharaoh if we live through this:
1) "And then the wheel on the tower fell off and the whole thing toppled over on their troops. Shoddy Babylonian workmanship."
or
2) "And then god Seth answered my prayers and smited the tower with thunderbolts. Or Ra has given me power to burn them with light."
I'm guessing 1.
Precisely.
If we live through this. Let's focus on living through this and cross that bridge when we reach it. I'll admit that it would be tougher to explain if we use powers of elemental manipulation so overtly, but we needn't start flinging fireballs all over the place.
Although perhaps we could come up with something clever with telekinesis. I don't want to keep ragging on A, and I'd like to be a bit more constructive, so how about this: we can tell our men that our mighty sword can also function as a boomerang, or that we're such a great warrior that the sword will return to us when thrown. So while we're sitting back on the battlements so we don't get hurt even worse than we are now, we launch the sword in an arc, to carve up the siege tower while it's going through traps, then have it return to us. It's far-fetched, but at least it has a mundane explanation.
Here's the problem I have with this argument: you presume that in our weakened state telekinesis will fail to do anything useful against the tower, but B or C will still work as intended. Why? At least we have some prior experience with telekinesis. With B or C absolutely none whatsoever. How do you know they will be useful or work at all?
But we already know the basics of elemental manipulation. C is a wild card, which is why I flopped to B.