The correct answer is D. Other records may have been lost; language is often a barrier.
Explanation:
According to grammar each punctuation mark including commas (,), colon (:) or semicolon (;) follow strict rules related to the situations or contexts in which each of them can be used. In the case of the semicolon (;) this punctuation mark is used to separate two independent clauses (clauses that express a complete thought) that are related, also semicolon is used in lists containing long items or before certain linking words such as however or consequently. In this case, the semicolon is being used to separate two independent clauses, the first clause is "Other records may have been lost" containing a subject, verb and complement and expressing a complete idea and the second one "language is often a barrier" with the same grammatical elements and also, expressing a complete idea, additionally semicolon is used as both clauses are related probably because language is the cause of records being lost. In this way, answer D. is correctly punctuated as the semicolon is being used to separate independent clauses, which is grammatically correct.
