1 + $$\tan^2\theta$$
=1+$$(sin^2\theta)/(cos^2\theta)$$
=
$$(cos^2\theta+sin^2\theta)/cos^2\theta$$
=$$1/cos^2\theta$$
(we know that$$sin^2\theta+cos^2\theta=1$$)
=$$sec^2\theta$$.
($$cos\theta=1/sec\theta$$)
B is correct choice.
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