22. The base of a solid is the region enclosed by the ellipse 4x^2+y^2=1. If all plane cross sections prependicular to the x-axis are semicircles, the its volume is

(A) Pi/3

(B) Pi/6

(C) Pi/2

(D) 2Pi/3

(E) Pi/4

23. If F(x) = (Sinx)^2/(1-cosx) then F'(x) =

(A) cos x

(B) Sin x

(C) -Sin x

(D) -cos x

(E) 2cosx

24. If dy/dx= y cos x and y=3 when x=0 then y=

(A) e^(sinx)+2

(B) e^(sinx) +3

(C) sinx +3

(D) sin x +3e^x

(E) 3e^(sin x)