A John explained yesterday that he had been working on that project for two weeks, but he can't finish it before the next Monday because his colleagues aren't helping him.
B John explained yesterday that he has been working on this project for two weeks, but he can't finish it before next Monday because his colleagues aren't helping him.
C John explained yesterday that he had been working on this project for two weeks, but he couldn't finish it before the following Monday because his colleagues weren't helping him.
D John explained yesterday that he had been working on that project for two weeks, but he couldn't finish it before the next Monday because his colleagues weren't helping him.
E John explained yesterday that he had been working on that project for two weeks, but he couldn't finish it before the following Monday because his colleagues hadn't helped him.