I believe the correct answer is A) From crest to crest.
~Silver
Answer:
A) - 1.8 m/s
Explanation:
As we know that whole system is initially at rest and there is no external force on this system
So total momentum of the system must be conserved
so we will have

now plug in all data into above equation



so correct answer is
A) - 1.8 m/s
A
method of procedure that has characterized natural science since the
17th century, consisting in systematic observation, measurement, and
experiment, and the formulation, testing, and modification of
hypotheses