Answer:
D. -3 + 6
Explanation:
Starting from zero, we move 3 units to the left. This gives -3.
We now change direction and move to the right 6 units. This gives +6.
Putting the two movements together gives
![- 3 + 6](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ctz36mrdv4hzmyihj2z1v4ng20bmf4dt6l.png)
The correct choice is D.
Note that moving to the left is considered to be negative while moving to the right is considered positive.