Choose the best item among A, B, C or D to complete the sentences

Choose the best item among A,B,Cor D to complete the sentences 
1. There used to be fewer people and ................... on the roads
A. roofs            B. helmest               C. helicopters                  D. vehicles
2. Do you know the .................. in the UK is to keep to the left?
A. traffic light                B. traffic rule                  C. traffic jam                  D. speed limit