States now have an incentive to lower the blood alcohol level that constitutes drunk driving by a federal law that withholds highway funds from those states that don't enforce the applicable standard.

a) that constitutes drunk driving by a federal law that withholds
b) that constitutes drunk driving, because a federal law withholds
c) that constitutes drunk driving, because a federal law withheld
d) which constitutes drunk driving by a federal law that withholds
e) which constitutes drunk driving, because a federal law withholds

That is restrictive and Which is nonrestrictive. Could someone explain?