~ Answer ~
You need to think about what would fit in the sentence best.
Tip: Try looking at all the answers, and reading them in the blank space.
For Example - The drivers " am " driving too fast on this road.
Now, i'm not saying that the example problem is right. All i'm doing is showing an example of what you should do with the rest of (a) through (d).
So, if you read the example problem you would have noticed it didn't sound right.
The correct answer would be (c), are.