Aimee is taking a shot of several deer in the forest. She wants to emphasize the size of those deer closest to her. Which lens should she use

This is the concept of trigonometry;
We are required to use the function y=9sec theta to solve the question.
Given the y=9sec theta,
where;
y=distance
theta=angle=65
the length of the beam will be calculated as follows;
From the trigonometric rules;
sec theta=1/cos theta
therefore our function can be written as:
y=9/cos theta
y=9/(cos 65)
y=9/0.4226
y=21.2958
y=21.3 ft (1 d.p)

therefore our answer is B. 21.3 ft