ETS PP test1 grammatical questions, please help me.

[LouisLin]

I practiced ETS PP test1 grammatical test and encountered these below questions. I hope some people can help me solve these problems. Thank you very much.

61. At the time of Columbus’ voyage, Native Americans used an astounding diversity of language,______ the diversity used by Europeans.
A. the greatest by far
B. by far than greater
C. by far the greatest
D. greater by far than

Why answer is D?

86. The Milky Way is a flat spiral galaxy who contains an estimated 100 billion stars,
including the Sun.

I know “who” is wrong, it should replace by “which”. However, I don’t know why “an estimate” is correct and why use an indefinite article before “estimated”.

121. Importance as foods, carbohydrates supply energy and are used to make fats.

Why answer is that “importance” is replaced by “important”? In addition, what is mean of “as” in the above sentence?

135. Is “the 1880’s” the same as the people lived during 1880’s

140. It is said that no potential frontier has such fired the imagination or challenged the ingenuity of humankind as has space.

I only knows the usage of “so as to+V”.
In addition, so+adj…..that+NC; such+N/NP…..that+NP

Why answer is that using “so” to replace “such”?

[maxim]

I practiced ETS PP test1 grammatical test and encountered these below questions. I hope some people can help me solve these problems. Thank you very much.

61. At the time of Columbus’ voyage, Native Americans used an astounding diversity of language,______ the diversity used by Europeans.
A. the greatest by far
B. by far than greater
C. by far the greatest
D. greater by far than

Why answer is D?
D is because there is a comparison: diversity of language > diversity used by Europeans


121. Importance as foods, carbohydrates supply energy and are used to make fats.

Why answer is that “importance” is replaced by “important”? In addition, what is mean of “as” in the above sentence?

importance - > it is important as

135. Is “the 1880’s” the same as the people lived during 1880’s

it is the generation of the 1880's = people

[vjlenin]

61: there is a comparison: so "GREATER THAN" should be in the answer. so
D.
86: AN ESTIMATED is a common usage. it doesn't refer to certainty,
notice. It's 'AN' estimate, and there are several estimates.
121: importance is noun. The sentence must begin with an adj since the
function of adj is used at the start. So it must be Important as-
meaning the subject of the sentence, carbohydrates, is as important
as foods.

140: study such that and so..that carefully u will know.
such is never used in such...that way. such that is similar to so that not so...that.