Step 1: Understanding the vehicle number plates and their colour codes.
Each colour on the vehicle number plate signifies the type of vehicle. Green plates are generally used for private vehicles, yellow for commercial vehicles, and black for defence vehicles.
Step 2: Analyzing the options.
(A) R is a private vehicle: This is incorrect because the plate colour used for R is yellow, indicating it is a commercial vehicle.
(B) P, S & U are private vehicles: This is correct. The green colour code on these plates indicates that they are private vehicles.
(C) Q, R, T & X are commercial vehicles: This is incorrect as X has a black plate, which indicates it is a defence vehicle, not a commercial one.
(D) X is a defence vehicle: This is correct as X has a black plate, which is typically used for defence vehicles.
Step 3: Conclusion.
The correct answers are (B) and (D) based on the colour codes for the different types of vehicles.