Question

Which sentence contains an error of agreement

the water was clear, blue, and beautiful
at first I stepped over the garbage on the street, but then I went back and picked it up
Pilots spend many years of their lives in training
He don't know what he's talking about

Answer 1

The first sentence says that the water was clear and blue, but you can't have water that is both clear and blue. It must be one or the other.

Answer 2

The last sentence is wrong, it has bad grammar