1)A wave created when two different waves meet will have an amplitude greater than the individual waves because of.

A)destructive interference
B)constructive interference
C)antinodes
D)a change in boundary

I got B

2)If a wave has a period of .02 seconds and a speed of 4 m/s, what is its wavelength?

.08 m

3)The Doppler effect is a change in the ______of a sound.

pitch

yes, on all three, on the third, I would use the term frequency, or apparent frequency. Pitch is ok.