Hi. I've been stuck on this multiple choice question for days now. I've managed to narrow it down to two answers but both seem right.?

Question: Is there such a thing as 'Incompressible Aerodynamics'?

A. No, as air is a gas and as such is always compressible. Density changes are always dominant and therefore it can't exist

B. Yes, but only if the flow speed is low enough, so the changes in density can be neglected. This is the case for Mach numbers below 0.3.

In my opinion both answers are correct as, in theory, it does exist but in reality it can't exist as the density is never constant, but, as it is a multiple choice question, only one answer can be correct.

I would be very grateful if someone could help me on this as I just can't seem to come to a conclusion..