Hector went to the grocery store by heading due north at 3 m/s, then turning east and continuing at the same speed for another three blocks. Which of the following is true about Hector's velocity?
A. Hector's velocity did not change because his direction did not change.
B. Hector's velocity changed because his speed changed.
C. Hector's velocity changed because his direction changed.
D. Hector's velocity did not change because his speed did not change.