Which of the following best represents the speed of Halley's comet when it is nearest to Earth?
a.1 × 10^-5 kilometers per year
b.1 × 10^5 kilometers per year
c.1 × 10^-5 kilometers per hour
d.1 × 10^5 kilometers per hour
a.1 × 10^-5 kilometers per year
b.1 × 10^5 kilometers per year
c.1 × 10^-5 kilometers per hour
d.1 × 10^5 kilometers per hour