[单选题]
The speed of Halley's Comet,zy4;32vvf bl (,rh cps while traveling in its elliptical orbi c,5 arbb /y;2o.mkgsbt around the S,ykr o5cmb b2s/g ab;.un,
A. is constant.
B. increases as it nears the Sun.
C. decreases as it nears the Sun.
D. is zero at two points in the orbit.
