laboratory rats

[bruno.shinjo]

Hi there!

I always thought that the structure "COMMA + BUT" would create an independent clause and require a subject. Therefore, the sentence provided would be something like "a dose of aspirin suffices, (...),but IT does interfere". Is it wrong to think it this way?

Thanks!

[thanghnvn]

I agree with sunny.jain

The main problem is parallelism

(C) a substance that promotes blood clotting, but does not seriously interfere

X that does Y, but does not Z

(D) which is a substance to promote blood clotting, but does not seriously interfere

X is to Y but does not Z

C is more parallel.

IMO Another problem is that D changes the meaning

option C says that the substance itself promotes blood clotting. On the other hand option D says that the substance is to promote blood clotting. In other words, somebody/something uses the substance to promote blood clotting. The latter is not the intended meaning of the sentence.

nah. you're making the wrong comparison.

the meaning of the sentence is:
aspirin blocks X (X is a substance that promotes clotting)
BUT
aspirin does not interfere with the production of Y (Y is a substance that prevents clotting).

in other words, in the correct answer choice, the structure is actually like this:
In laboratory rats, a low dose of aspirin usually suffices to block production of thromboxane, a substance that promotes blood clotting, but does not seriously interfere with the production of prostacyclin, which prevents clotting.

so, parallelism is not the key differentiator between (c) and (d).

--

there are two problems i see in (d).

--

problem #1

a substance to promote... is unidiomatic.
the only context in which i can remember "a NOUN to VERB" is a context in which the NOUN is abstract in nature. for instance:
a way to produce goods
a reason to try harder
etc.
note that "substance" is a concrete item; it's not an abstraction like "way" or "reason".

if you're talking about concrete objects, you should replace the infinitive with something else. for instance:
* a substance to promote X (incorrect) --> a substance that promotes X (correct)
* a tool to install the shelves (incorrect) --> a tool with which to install the shelves (correct)

--

problem #2

"which is" is unnecessary and ugly.

if "which is" is followed by a description of something, you should just omit it, producing an appositive modifier:
X, which is a substance... (ugly) --> X, a substance... (better)
Person X, who is the coach of Team Y (ugly) --> Person X, the coach of Team Y (better)

etc.

we can not remember that abstract noun can go with "to do'and concrete noun can not go with "to do" in above pattern. what we can remember easily is that in the pattern "noun +to do" , the noun may or may not incur the action of "to do". but in the patter " noun+doing/that do", the noun clearly incur the action of "doing/that do". this is the main difference and luckily is easy to remember in the test room.

is my thinking correct?

[RonPurewal]

we can not remember that abstract noun can go with "to do'and concrete noun can not go with "to do" in above pattern. what we can remember easily is that in the pattern "noun +to do" , the noun may or may not incur the action of "to do". but in the patter " noun+doing/that do", the noun clearly incur the action of "doing/that do". this is the main difference and luckily is easy to remember in the test room.

is my thinking correct?

I'm unable to follow this. Please provide specific examples.
Thanks.

[amank196]

I still find the explanations about D being wrong hard to follow is there any other way to eliminate D apart from being "unidiomatic" thanks!

[RonPurewal]

well, you should understand this idiomatic use of "to + verb".
"a substance to promote..." doesn't make any sense, because it implies that there's some sort of GOAL or PURPOSE that the substance has in mind. clearly, substances can't have goals or purposes of their own, so that's nonsense.

__

as far as eliminating D, though—
you should be able to eliminate D strictly on the grounds of non-parallelism.

there are 2 parallel ideas:
• promotes blood clotting
• does not interfere with xxxxx other stuff

these things clearly MUST be expressed in parallel forms. in choice D they aren't... so choice D is incorrect. end of story.

(there's no point in trying to claim parallelism between "is a substance..." and "does not interfere...", since those are clearly THE WRONG THINGS to put in parallel.)

[amank196]

Thanks Ron! You are the man!

[RonPurewal]

you're welcome.