HELP!!!!

Two waves are traveling towards each other. One wave is a trough of amplitude 2.4 mm, the other is a trough of amplitude 4.6 mm. What will be the result of these waves intersecting?

Select one:

a.
a trough of amplitude 2.2 mm

b.
a crest of amplitude 2.2 mm

c.
a crest of amplitude 7.0 mm

d.
a trough of amplitude 7.0 mm