Any help will be appreciated.
1. Not until the eighteenth century------------ the complex chemistry of metallurgy
(A) when scientists began to appreciate
(B) did scientists begin to appreciate
(C) scientists who were beginning to appreciate
I think its a negative type inversion,therefore auxially verb should be preceded by the subect like here in this case did is preceded by scientists in option B.

2. .......... 1810, water-powered textile manufacturing arrived in New Hampshire with the founding of a company in Manchester that manufactured cotton and wool.
(A) Early
(B) In the early
(c) As early as
(d) When early
Whats wrong with the option B?

3. Lichens grow extremely well in very plants can cold parts of the world survive.
(A) where few other
(B) few others
(C) where do few others
(D) there are few others

This problem went over my head.

4.[Native to] South America and [cultivated] there for thousands of years, the peanut [is] said to[ have introduced] to North America by early explorers .

Hmmmm something wrong there with have introduced?

5-Among the symptoms of measles, which takes about twelve days to incubate, [are] a high fever, swelling of glands in the neck, a cough, and sensitive to light.
Something wrong with are in the sentence.

6 -There are about 350 species and subspecies of birds in danger of become extinct, with a large number of them, 117 in all, found on oceanic islands.
oh well I thought the problem is with the pronoun them? but my key says become is wrong. My key might be wrong?
At the risk of sounding too complicated, Atesttaker, here's my response. I hope it will help until someone who can put things in simpler ways comes. Emotion: smile

1. You got that one right. "B" is correct, and so is your explanation.

2. "C" is correct. It means something like "as far back as 1810" (a long time ago).
If you want to use "B", perhaps "At the beginning of 1810" would sound better.
You can say "in the early 19th century", for example, or "in the early 1810s".
However, with "as early as 1810", the meaning of the sentence is different from the one you proposed.

3. That sentence lost me too. It wouldn't make any sense even if we replaced some part of it with one of the constructions provided. "can cold parts of the world survive" has no meaning to me.
Hopefully someone else will enlighten us.

4. Yes, there's something wrong with [have introduced] in that sentence. "have been introduced" is correct, it is a sentence with a verb in passive voice (you always need some form of "to be" in order to construct a passive sentence).
"Peanut is said to have been introduced to North America by early explorers."
Compare that with the corresponding active sentence:
"They say that early explorers introduced peanut to North America."

5. "sensitivity to light" instead of "sensitive". "Sensitive" is an adjective, and you need a noun in that construction.

6. The pronoun "them" is ok. The problem is "danger of become extinct". The general rule says that when we use a verb after a preposition, we need an -ing form.
"danger of becoming extinct" is correct.

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That put a smile on my face,Miriam. You are in no way complicated but rather different.. I have gotten the mistakes and thanks for the help.
Anyone noticed that this site was down lately or the problem was for me only.I was trying to open it but all my efforts were in vain.Thanks its back.
You're welcome, Atesttaker. Emotion: smile
And yes, it seems the forums were down yesterday. Fortunately, everything seems to be back to normal now.