Researchers agreed that the study of new treatments for heart attack patients was extremely important but more research was needed to determine that balloon angioplasty preceded with ultrasound was not any better for heart attack patients than the balloon procedure by itself. (C)that more research was needed to determine whether balloon angioplasty preceded by ultrasound is any better for heart attack patients than (D)that more research was needed to determine whether balloon angioplasty preceded by ultrasound was any better for heart attack patients than 这题的正确答案是C,但是我觉得应该是D啊,这两个选项的差别在于后面的is 和was,根据时态,我觉得应该是D, 求解!