Answer:
A
Step-by-step explanation:
As highlighted in the DMV handbook,
"Speed limit" signs are used to indicate the legal maximum speed at which a vehicle may travel on a given road or highway.
The other answers imply you are allowed to go faster than the speed limit, which is untrue. The speed limit is the maximum you are allowed to go, you are allowed to travel under it so long as you do not block the reasonable flow of traffic.
Another hint is the usage of the word limit. Limit implies it is capping of something.