Answer
$4\rightarrow C$
Work Step by Step
$\tan ^{2}x+1=\dfrac {\sin ^{2}x}{\cos ^{2}x}+1=\dfrac {\sin ^{2}x+\cos ^{2}x}{\cos ^{2}x}=\dfrac {1}{\cos ^{2}x}=sec^{2}x\Rightarrow $
$4\rightarrow C$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.