Hi there, I was told, in separate occasions, by two native English editors (one Ph.D in biochem, the other Ph.D in American literature; so I guess this is pretty true) that my sentnece: The expressions of collagen-I, collagen-III, and osteopontin were relatively stable during the whole process of healing. should be revised into: The expression of collagen-I, collagen-III, and osteopontin was relatively stable ..... Can any one kindly advise why??? What is the logic here? Many thanks! By the way, the collagen and osteopon are just the names of proteins in bone.