Concept:
During tablet compression several defects can occur. Each has a precise definition, so this is a matter of matching the description to the correct term.
Step 1: The defect described is the separation of a tablet into two or more distinct horizontal layers. This is called lamination. It usually happens due to trapped air or over-lubrication, where the tablet splits into layers after compression.
Step 2: Distinguish from the others — sticking is when material adheres to the punch faces, capping is when the top (cap) of the tablet separates as a single dome, and mottling is an uneven distribution of colour on the tablet surface. Only lamination means separation into layers.
Answer: Option (2) — separation of one or more layers of a tablet is called lamination. (2)