The Voyager 1 spacecraft, shown below, completed its space exploration mission in 1980 and has since been traveling away from Earth at a speed of about 39,000 miles per hour.
If no unbalanced forces act on Voyager 1, then
A. the direction of its motion will reverse.
B. it will continue traveling at the same speed.
C. its speed will slowly decrease.
D. its speed will slowly increase.
