Burning fossil fuels - oil, coal, and natural gas - causes pollution.

Burning fossil fuels causes pollution.
Env manager has proposed replacing diesel vehicle with electric or solar.
Management decided electric because they are cheaper (though hassle because craving points will need to be installed)

We need to undermine the decision of the management - decision of the management is aimed at reducing pollution with low associated cost.
We need to show why this goal is not being met with the decision taken (of replacing with electric vehicles)

A. Solar powered vehicles do not cause more pollution than battery powered vehicles.

This doesn't show why electric vehicles are not good enough to reduce pollution.

B. The chemical processes in the plant causes much higher pollution than that the diesel-oil driven vehicles produce.

Irrelevant. If there are some things that the plant cannot change, that doesn't mean it shouldn't change those that it can. Say 100 units of pollution is caused daily by the plant - 80 by chemical processes and 20 by vehicles. Because they cannot reduce the 80, doesn't mean they shouldn't cut down the 20.

C. The vehicles that go inside the chemical plant need to be fitted with costly spark-proof safety devices.

Doesn't give the difference between electric and solar. Does this make electric vehicles more expensive than solar? Do solar vehicles not need spark proof devices? We don't know.

D. A coal-fired power plant supplies electricity to the chemical plant.

This tells us that electric vehicles will indirectly still cause pollution because the power plant uses the fossil fuel - coal - to provide electricity. SO use of electric vehicle will just mean use of more electricity and hence burning of more coal. So in a way, electric vehicles also cause fossil fuel pollution. So the management's plan is flawed.

E. Other plants in the vicinity of the chemical plant will continue to use diesel-oil driven vehicles.

Irrelevant, just like (B). If all plants cause 1000 units of pollution daily and other 900 would be maintained as it is, doesn't mean this plant should not do what it can to reduce pollution. Overall pollution will go down even if only one plant takes steps.

Answer (D)