The correct answer is Option 2) i.e. but also"Not only.....But also" is correlative conjunction which are used in a pair. Correlative conjunctions are pairs such as neither . . . nor, not . . . only, and but . . . also. These conjunctions connect two balanced clauses, phrases, or words. The two elements that correlative conjunctions connect are usually similar in length and grammatical structure.This Conjunction pair (not only....but also) is used to present two related pieces of information. Both pieces of information are being presented by the writer as surprising or unexpected, with the second one being even more surprising than the first. The first piece of information(accused of theft) will be followed by the second one (conspiracy).Complete Sentence: He was not only accused of theft but also of conspiracy.