$\int\;\large\frac{1}{1+cos x} \;dx$

Question

$(a)\;tan(\large\frac{x}{2})+c\qquad(b)\;sec^2(\large\frac{x}{2})+c\qquad(c)\;\large\frac{1}{2}tan(\large\frac{x}{2})+c\qquad(d)\;2tan(\large\frac{x}{2})+c$