Option 1 states that both A and R are individually true and R is the correct explanation of A. Assertion A is that Muhammad bin Tughlaq left Delhi, living in a camp called Swarga-dwari for two years. Reason R is that Delhi was ravaged by a form of plague at that time, causing many deaths. As stated in option 1, both these statements are true. Muhammad bin Tughlaq indeed shifted his base temporarily due to problems in Delhi. At the same time, Delhi was suffering from plague which could justify Tughlaq`s move. Thus, Reason R could be accurate in explaining the action of Tughlaq described in Assertion A. Hence, option 1 correctly identifies that both statements are true individually and that R provides a valid reason for A.

To broadly break down the other options, option 2 suggests that the plague`s occurrence and Tughlaq`s move are true but unrelated. Option 3 suggests the plague did not occur, while Option 4 implies that Tughlaq never moved out from Delhi, which are factually incorrect.