The Fundamental Theorem of Welfare Economics tells us, roughly,

A) that high welfares are very important to the individuals who live in an advanced economy.

B) that you cannot have more of one thing without having less of at least one other thing.

C) that high welfares are important, but are not everything.

D) that an economic system with many buyers and many sellers in all markets will be maximally efficient.

E) that the existence of money is crucial if an economy is to achieve high incomes.