[单选题]
The speed of Halley's 28lg -wduo.2dt:pkvuw 0 s+5ymrq 4kqComet, while trw ou;hw;m iwik*8s0 blt:/ss3aveling in its elliptical orbit around the Suntuw0*;l i isokms; s3wb8 h/w:,
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.
