疑问：旧Prep2-43与“夹心现象”

yyyr

旧Prep2-43，这道题选对答案不算难，就不讨论了。
但是关于其中的“夹心现象”，还要请教大牛们。

在Prep语法笔记中提到过：
“v-ing... 形式放在句子中间，有可能作为伴随动作状语，同时向前和向后修饰引起歧义，要慎用。”

但对于这道题，语法笔记中说：
“这个句子中的分词结构 acting as...只能修饰 in that they reflect and absorb solar radiation，不存在歧
义。如果要往后修饰主句 they also accelerate...，那么必须在 Although...从句与 acting as...之间加上
连词，因为这都是修饰主句的状语（前者是状语从句，后者是分词结构状语），没有连词无法并列存在。”

我很不解，为什么两个状语之间一定要有连词呢？
一个句子中有多个状语，并不都有连词啊。（也未必就是并列的成分啊）
说“两个修饰主句的状语，没有连词无法并列存在”是什么原因呢？

另外，如果说非要有连词不可的话，那这里应该用什么连词呢？
although... and... ? although... but... ? 都说不过去啊。
假如没有适用的连词，那又为何说一定这里要有连词呢？

题目如下~
43. (26724-!-item-!-188;#058&003285)
Although ice particles in the upper atmosphere benefit Earth in that they reflect and absorb solar
radiation, acting as a global thermostat and thus keeping Earth from either burning up or freezing
over, they also accelerate the destruction of the ozone layer by reacting with chlorofluorocarbons
(CFC's).
(A) acting as a global thermostat and thus keeping Earth from either burning up or freezing over,
they also accelerate
(B) acting as a global thermostat and thus keeping Earth either from burning up or freezing over,
while also accelerating
(C) act as a global thermostat and thus keep Earth from either burning up or freezing over, while
also accelerating
(D) they act as a global thermostat that thus keeps Earth either from burning up or freezing over,
even though it also accelerates
(E) they act as a global thermostat to thus keep Earth from either burning up or freezing over, but
they also accelerate

赵小婕

同问！

记忆钢琴

期待NN解答

记忆钢琴

ding!

yyyr

求教！