If a sound wave speeds up and its frequency does not change, what happens
to the wavelength?

Wave speed, frequency and wavelength in refraction

Explanation:

Although the wave slows down, its frequency remains the same, due to the fact that its wavelength is shorter. When waves travel from one medium to another the frequency never changes. As waves travel into the denser medium, they slow down and wavelength decreases.

the answer to your question is:

c. complementary base-pairing

b.