关于having done 的解释 having done 做后置定语必错,但可以做伴随状语。 此题显然是做such life forms 的后置定语。 因为伴随状语通常有“,”隔开为标志如 1.Having finally reached a tentative labor agreement with its company's pilots, the airline's board of directors must now determine how the airline can both increase profits and compete more effectively for customers than it did in the past. 2.Some patients who do not respond to therapies for depression may simply have received inadequate treatment, having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon. 因此,A错。 此外,presume + n.也可以如 presume the e existence of life on other planets.但n.必须是动作性名词。实物名词life forms无意义,应加句子,因此A又错。选C
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