Which of the following statements are correct?1. The pair (AB) is controllable implies that the pair (ATBT) is observable.2. The pair (AB) is controllable implies that the pair (ATBT) is unobservable.3. The pair (AC) is observable implies that the pair (ATCT) is controllable.4. The pair (AC) is observable implies that the pair (ATCT) is uncontrollable.where: A, B and C are having their standard meanings

• A. 1 and 3 only
• B. 1 and 4 only
• C. 2 and 3 only
• D. 2 and 4 only