Option 1 contradicts the given statement which suggests minimizing the use of vehicles to reduce pollution. Option 2 cannot be inferred as the extent of the impact of pollution on the environment is indeterminate. This eliminates options 1 and 2. Now the given statement nowhere states that vehicles on the road are the only cause of pollution. Hence option 4 cannot be inferred. Thus after the elimination, we are left with option 3 which says the reduction of pollution can save the degrading environment. The second part of the given information can be considered as a measure to deal with the problem mentioned in the first part. Therefore option 4 holds logic and is an appropriate inference from the given fact.