Researchers agreed【that】 the study of new treatments for heart attack patients was extremely important but 【that】more research was needed to determine 【whether 】balloon angioplasty preceded by ultrasound is any better for heart attack patients than the balloon procedure by itself.
研究人员一致认为，对心脏病发作患者的新治疗方法的研究非常重要，但需要更多的研究来确定超声之前的球囊血管成形术是否比球囊手术本身对心脏病发作患者更好。

agree that…but that…，宾语从句的平行that不能省，使句子更加清晰

whether or not的使用：
在引导宾从的时候只能够用whether，而不能加or not，否则累赘；
在引导状从的时候必须加上or not，即whether or not。

determine的内容如果现在还未最终决定下来时， is用现在时成立

"错选B 没发现whether or not是重复的
determine that 错误 改变了原意 原文中determine后面的事情还不确定 排除ADE
C没选 主要是觉得少了助动词is 但是在这句话中少了is不会引起歧义。另外是觉得主语research不能发出to do的动作，但是在被动语态中这一点是例外。"

that省不省略都是一个意思，都可以

ps. A third "split" that could have guided your process of eliminate was the "more research" v. "that more research." Since the non-underlined portion of the sentence states "researchers agreed that," a second "that" is needed to maintain proper parallelism.

曼哈顿官方：The first "split" I noticed was "preceded by" v. "preceded with." As one thing is preceded by another, eliminate choices A and D. The second "split" I noticed was "needed for determining" v. "needed to determine." Idiomatically, needed to determine is correct. Eliminate B and E. The best answer is C.

C的确是后半句应该用was好于is，但是D项that 不对，和原句语意不符。语意/语法优先于时态。

d选项改变了句子意思，就是承认了第一种方法更优，而实际上uncertain

"whether or not" is almost always considered redundant on GMAT.

B is wrong because "is" is redundant

d选项解释多注意

determine的内容发生在主句agree之后，所以应该用agree向后推移的时态：一般现在时is，而不能用一般过去时was。

preceded by。。

preceded by

whether/that: Here we need to check/determine something. SO we need to use whether[or not], whereas in D it uses THAT showing that the result(the part after that) WAS true and now more research is needed to prove/reprove/verify its authenticity. Does this makes sense,meaning-wise?

c 的is的时态没有问题吗？？整句话不是都处于过去式中吗？

C中不补出is不会感觉是patents和balloon procedure在比较嘛？

1)is/was: u feel was is correct because you are looking at verb tense consistency. But u need to check the meaning also. In this statement, it just checks " whether X is any better[or not] "
2)whether/that: Here we need to check/determine something. SO we need to use whether[or not], whereas in D it uses THAT showing that the result(the part after that) WAS true and now more research is needed to prove/reprove/verify its authenticity. Does this makes sense,meaning-wise?

这个题难道不应该还有 “平行” 的知识点吗？因为最后有个 “than”， than 前后句应该平行

理解了句意后感觉determine后一定要出现whether这个词
b选项or not多余
c中前面的that一开始也被我拿来判断了…-。-

1，也就是说是否需要加that,在这个题目看来，既不是考点，也不具有逻辑意思上的错误。
2，总感觉balloon angioplasty 后面跟的preceded是错误的，因为未划线部分是balloon procedure，所以认为应该是balloon angioplasty proceeded,进行，进展的意思，这个时候用by似乎就可以了。而preceded的意思是先于....之前......用by的话，逻辑意思上不搭调啊.