Positive/Negative - Trigo

Suppose $\displaystyle a\neq \cfrac { k\pi }{ 2 }$ for any integer $k$ and

$\displaystyle T=\cfrac { \sin { a } +\tan { a } }{ \cos { a } +\cot { a } }$

Which of the following statements is true?

(A) T takes negative values only.

(B) T takes non-negative values only.

(C) T takes positive values only.

(D) T takes both positive and negative values.

AYWC?