instruction:
Given a scientific question, generate a correct answer to it.
question:
Many microorganisms are single celled and use what for perception and movement?
answer:
organelles

question:
In frequency, the larger the air column, the larger the what?
answer:
wavelength

question:
Of course, a net external force is needed to cause any acceleration, just as newton proposed in his second law of what?
answer:
motion