5
7
3
None of these
Answer is Right!
Answer is Wrong!
The correct answer is C. 3.
A mixed train is a train that carries both freight and passenger cars. The maximum number of explosive unit wagons in a mixed train is 3. This is because explosive unit wagons are considered to be dangerous goods, and there are restrictions on the number of dangerous goods that can be carried on a train.
Option A is incorrect because 5 is more than the maximum number of explosive unit wagons that can be carried on a mixed train.
Option B is incorrect because 7 is more than the maximum number of explosive unit wagons that can be carried on a mixed train.
Option D is incorrect because it is not one of the possible answers.