If you've waited more than five minutes at a yield sign,
a. you may proceed even if it means another driver must slow down for you
b. you must keep waiting if it means another driver must slow down for you
c. you must proceed no matter what because there are other drivers behind you d. you must proceed rapidly so no driver must slow down for you

A. you may proceed even if it means another driver must slow down for you.

Explanation:

To "yield" means that you have to stop for a little while or slow down in order to let another vehicle move before you. Sometimes, you might see a yield sign at highway entrances or rotaries. When this happens, you must stop or slow down so you let the flow of traffic continue. However, if you have stopped at a yield sign for more than five minutes, then you may proceed, even of it means that another driver must slow down for you.