The number of undergraduate degrees in engineering awarded by colleges and universities in the United States increased by more than twice from 1978 to 1985.
The number of undergraduate degrees in engineering awarded by colleges and universities in the United States increased by more than twice from 1978 to 1985.
In the original sentence, "increased by more than twice" is unidiomatic; when numbers increase, they "increase by more than a factor of two." Also, "twice" is an adverb; only nouns can follow the preposition "by."
Answer choice (B) introduces an issue in meaning. When the number of degrees "increased more than two times," that means over the period of 1978 to 1985, it has gone up at least twice: maybe in 1980 and then in 1981. The other times, it has stayed steady or gone down.
In answer choice (D), "was more than" demonstrates a comparison: "The number of pennies was more than the number of nickels." It doesn't make sense for us to say "the number ... was more than doubled": we cannot compare "number" with "doubled" since doubled is not a noun.
The past perfect tense "had more than doubled" in (E) is not justified. The past perfect is used when there is a comparison between one past action with another past action (or past time marker). In this sentence, we're not comparing "the number ... had ... doubled" with any other time reference.
(C) is correct because "doubled" is used correctly in the simple past.