C is the correct response because the law requires parents to put children under four years of age in car seats.

Here is why the other answers are incorrect:

A. This sentence would mean that the parents should sit in a child safety seat if the parents have a child who is younger than four years old. This isn't right because parents don't sit in child safety seats.

B. Although the wording is different, this sentence is identical in meaning to sentence A. And so the reasons that it is incorrect are the same as A too.

D. This sentence would mean that parents should try to restrain their children so that they remain under four years of age by keeping them in a car seat. Although I'm sure that some parents would prefer to keep their kids as cute babies rather than rebellious teens, you really can't keep children from getting older. 8)

E. This sentence would mean that parents should: 1) try to restrain their children so that they remain under four years of age and 2) sit in a child safety seat while doing so. Again, parents can't really stop their children from getting older. Additionally, parents shouldn't sit in child safety seats.

cool explanation

thanks!