I would say ten or five but it is not specific enough to have a correct answer.
Answer:
2
Step-by-step explanation:
From the graph, we obtain the trigonometric function as:

The corresponding cosine function have equation.

This function is of the form: 
where
is the amplitude.
Therefore the amplitude is |2|=2
The third choice is correct
Answer:
b
Step-by-step explanation:
2nd one is the correct one I think