If the acceleration of an object is constant, which of the following must be true?

1. The velocity-time graph is a horizontal line.
2. The position-time graph is a horizontal line.
3. The velocity-time graph is a straight line.
4. The position-time graph is a straight line.

1. C
2. D
3. A,C
4. A,C,D
5. B,C,D