Error correction

Under( the certain )conditions, a rainbow appears at the end (of) a( rain shower)
A B C
(in the quarter) of the sky opposite the Sun.
D

Mr. Micawber has taught me before that the determiner 'the' before a word in the plural form is generally unnecessary. But I do see some words in the plural form have their determiners - 'the'.

So, in this question, is choice A wrong?

Thanks a lot, CJ.

But I have another question I haven't gotten the specific answer. I hope you allow me to post here. (Sorry I should've started it as a new thread for you people to track it more easily, but I've already created one about this before. And NON C took the time to respond it. I really appreciate it. But he didn't give me the specifics. And he seems very busy these days. He didn't respond to my post any more.)

Here's the quote,

The question goes like this, "Fibers of hair and wool are not continuous and must normally be spun into thread _____ woven into textile fabrics. (A) when to be (B) if they are to be" Now I got stuck here. It's easy to tell B) sounds better though. However, when you look at A) for a while, you will find it's OK too. 'Cause there's a grammatical rule that states "it's/they're.." after when can be omitted. Anyway, 'when' seems better to me than 'if' here. So... I really got caught in the dilemma. Hope you can help me out.

(In addition, the answer is B. I just want you to convince me that the choice A is wrong.)

Thak you!!

The children are happy when are playing

Dear Roadrunner,
Why didn't you leave are out together with they ? Then it will be like,
'The children are happy when playing.'

It's the same as the choice A,
'Fibers of hair and wool are not continuous and must normally be spun into thread when (they are) to be woven into textile fabrics.'

That's why I posted this question twice, RR. But don't worry. We have super-moderators here.

Anyway, thank you so much.

That is a rather aggressive statement!
Some of us have real jobs and only answer posts in the little spare time we have. I hope you will continue to be considerate and understanding on this point.

Now let's get to your question. I'm going to add a third choice to make it more interesting.

"Fibers of hair and wool are not continuous and must normally be spun into thread _____ woven into textile fabrics.
(A) when to be
(B) if they are to be
(C) when

The answer is (B). It says that the fibers must be spun into thread (first) if they are going to be used to make fabrics - if they are going to be woven into fabrics (later).

(A) is clearly wrong. "when to be" is not a grammatical expression here. The point you make about omitting forms of "to be" after "when" would mean that the "to be" should be omitted. That would lead us to choice (C).

Choice(C) is the second best of the three, but, of course, it was not a possible choice in the original problem. It says that the fibers must be spun into thread when woven (i.e., at the same time as they are woven) into fabrics. It is certainly possible to use this sentence, but it means something ever so slightly different from the one which comes from (B). The difference is in the fine points of the time sequences implied.

Calif Jim