The effect of the new policy, which aimed to reduce urban traffic, were immediately apparent.

The effect of the new policy, which aimed to reduce urban traffic, were immediately apparent.

1. A.The effect of the new policy, which aimed to reduce urban traffic, were immediately apparent.
2. B.The effect of the new policy, which aimed to reduce urban traffic, was immediately apparent.
3. C.The effects of the new policy, which aimed to reduce urban traffic, were immediately apparent.
4. D.The effect of the new policy, which aimed to reduce urban traffic, is immediately apparent.