Verified answer

Higher due to dopler effect.

as the bat is approachig the wall, according to Doppler's effect , the frequency received should be higher than its emitted frequency.

I am guessing the same. It is time that is important to th bat.

Doppler is a sound passing you. It is high in comparision to when it passes.

The bat gave a high frquenc to start with.The same.

Then again it is moving in the same direction

same.