我来把解释打上吧~ The single subject of this sentence is Halley's Comet, and its single verb pharase is did cause. The comparison presented by the sentence is between adverbial phrases describing times when the comet was seen. Grammatically, the items being compared are parallel prepositional phrases beginning with the preposition in: in no other sighting and in its return in 1910-1911. This is the clearest, most economical way of presenting the information. The options that introduce a second verb(did or had)biolate the parallelism and introduce a comparison between the comet itself(subject of the verb did cause)and the comet's return(subject of the verb did or had) A this sentence implies a comparison between the comet and its return. B this sentence implies a comparision between the comet and its return; had is the wrong auxiliary verb form because it must be followed by caused instead of cause C correct D this sentence implies a comparision between the comet and its return. E this sentence violates parallelism, impleying a comparison between a prepositional phrase and a noun phrase. |