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3. Health officials estimate that 35 million Africans are in danger of contracting trypanosomiasis, or "African sleeping sickness," a parasitic disease spread by the bites of tsetse flies.

　　(A) are in danger of contracting

(B) are in danger to contract

(C) have a danger of contracting

(D) are endangered by contraction

(E) have a danger that they will contract

4. Unlike a funded pension system, in Which contributions are invested to pay future beneficiaries, a pay-as-you-go approach is the foundation of Social Security.

　　(A) a pay-as-you-go approach is the foundation of Social Security

　　(B) the foundation of Social Security is a pay-as-you-go approach

　　(C) the approach of Social Security is pay-as-you-go

　　(D) Social Security's approach is pay-as-you-go

　　(E) Social Security is founded on a pay-as-you-go approach

Answer：

3. Choice A, which is both idiomatic and concise, is best. In choice B, to contract is wrong because the phrase are in danger must be followed by of, not by an infinitive. The phrase have a danger is unidiomatic in C. In D, the phrase by contraction trypanosomiasis requires of after contraction; even if this correction were made, though, the passive construction in D would be unnecessarily wordy and also imprecise, because it is the disease more than the act of contracting it that poses the danger. In E, have a danger is again unidiomatic, and the to that clause following the phrase is, within the structure of the sentence, ungrammatical and awkward.

4. In this sentence, the first noun of the main clause grammatically identifies what is being compared with a funded pens ion system; to be logical, the comparison must be made between comparable things. Only E, the best choice, compares one kind of system of providing for retirees, the funded pension system, with another such system. Social Security. Choices A, C, and D all illogically compare the pension system with the approach taken by Social Security itself. In B, the comparison of pension system with foundation is similarly flawed.

延伸阅读：

SAT语法练习题及解析（三）

SAT语法练习题及解析（四）

SAT语法练习题及解析（五）

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