John isn’t intelligent so he can’t do the test well. -> If John..................
Giải thích
John isn’t intelligent so he can’t do the test well.
-> If John were intelligent, he could/ would (would be able) to do the test well/ better.
John isn’t intelligent so he can’t do the test well.
-> If John were intelligent, he could/ would (would be able) to do the test well/ better.