A great deal of research into the possible causes of cancer.

are being done

have been done

has been done

has done

Question

Английский язык: A great deal of research into the possible causes of cancer.are being donehave been donehas been donehas done​

4okoladka100 · Answer

Has been done Объяснение:...

A great deal of research into the possible causes of cancer.are being donehave been donehas been donehas done​