The answer is indeed letter D. A full lunar eclipse lasts longer than a partial eclipse.
Explanation:
In the sentence "A full lunar eclipse lasts longer than a partial eclipse" we can find an adverb, "longer", modifying the verb "lasts". The adverb itself is also modified by an elliptical adverb clause, "than a partial eclipse". This clause is elliptical because the verb that should appear in it is implied - the regular clause would be "than a partial eclipse lasts/does".
it is appropriate to break the rule that requires subjects joined by and to use a plural verb when either and neither are subjects. They always take singular verb.
