跪求高人解答，关于时态一直的题。

Hsu哇哇

Researchers agreed that the study of new treatments for heart attack patients was extremely important butmore research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than the balloon procedure by itself.
A. more research was needed to determine that balloon angioplasty preceded with ultrasound was or was not any better for heart attack patients than
B. more research was needed for determining whether or not balloon angioplasty preceded by ultrasound is any better for heart attack patients than is
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 that balloon angioplasty preceded with ultrasound was any better for heart attack patients than
E. that more research was needed for determining that balloon angioplasty preceded by ultrasound is or is not any better for heart attack patients than is



为什么我感觉C从句后面用is怪怪的啊，它的主句不是过去式么，后面的从句不应该也是过去时态么？求问D为什么不对。

greygray

科学研究里常常过去式+现在时的，比如：
scientists found out that Earth is more than 4.5 billion years old
后面是科学现象，用一般现在时表述

Hsu哇哇

greygray 发表于 2013-12-15 14:03
科学研究里常常过去式+现在时的，比如：
scientists found out that Earth is more than 4.5 billion years ...

因为是客观事实是吧？

greygray

Hsu哇哇 发表于 2013-12-15 17:54
因为是客观事实是吧？

是滴，就是这样

Hsu哇哇

greygray 发表于 2013-12-15 18:06
是滴，就是这样

many thanks