The word "dust" appears only in the second sentence, so the digit that doesn't appear in any of the other codes must represent "dust." The digit that fits this criterion is 5.
So, the correct option is (C): 5.

A, B, C, D, E, F and G are travelling in three different vehicles: Swift, Creta, and Nexon. There are at least two passengers in each vehicle. Among them, only two are male. There are two engineers, two doctors and three teachers.
(i) C is a lady doctor and she does not travel with A and F, who are sisters.
(ii) B, a male engineer, travels with only G, a teacher, in a Swift.
(iii) D is a male doctor.
(iv) Two persons belonging to the same profession do not travel in the same vehicle.
(v) A is not an engineer and travels in a Creta.
(vi) The pair of sisters A and F travels in the same vehicle.
What is the profession of F?