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（A）

(E) have a danger that they will contract

这道题og的解释中说the passive construction in D would be unnecessarily wordy and also imprecise, because it is the disease more than the acting of contracting it that poses the danger 这句话完全不明白为什么。 还有in E, the that clause following the phrase is , within the structure of the sentence, ungrammatical and awkward?也不明白 请指教