anyone good at economics please assist?

[Anjaree]

1 B is correct. Positive externalities mean that the marginal private cost is smaller the marginal social benefit, so that the subsidy should fill the gap. But as it said MBA graduate will get more higher wage, and also the subsidy from the State, the marginal private benefit will exceed the marginal social benefit. The equilibrium will be greater than usual positive externalities.
2. D is correct.
a is correct because it will shift supply to the left, price will increase and pollution will decrease.It does not need a State's control like regulations.
b is correct.I guess it is not population,but pollution. An increase in price will decrease demand. And in the case of elastic demand, the decrease in quantity and pollution even more.
c. tax will raise revenue for the government. The quota and regulation do not.