toefl test 1 structure q26 to 30

toefl test 1 structure q26 to 30

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26 

............ aluminum is exposed to oxygen,a tough,invisible oxide

forms,making it extremely corrosion-resistant

No sooner than

Once << R

So soon that

The sooner

Explanation

"Once" is used in an adverb clause to show time relationship. 

The meaning of "once" is similar to "when."

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27

 .......... the silurian period,there was significant radiation of

rapacious fish equipped with bulky jaws

When

Since

Until

During << R

Explanation

A time preposition is needed here. Although all the choices deal with time,

 only "during" is the correct answer; it emphasizes a point in time.

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28 sickle-cell anemia,which is a gentic defect,is caused

by .......... that encourages a faulty form of hemoglobin

mutant a certain allele

a certain mutant allele << R

a mutant allele certain

an allele certain mutant

Explanation

This question is based on the correct word order. Only (B) has the right order.

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29 

mary mcleod bethune,a leading african-american ..........,

as a child attended the local free school

educator who

educator  << R

educator she

whose education

Explanation

The noun "educator" is needed to modify the adjective " a leading African-American."

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30

 beryllium is used as a bonding agent for nuclear fuel

elements ......... toughness and excellent resistance to heat

although its

it is when

that its

because of its << R

Explanation

"Because of "is a preposition that is followed by a noun object; it is used to show a reason.

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