The correct option is
C 1, 3, 5-trimethylbenzene
When acetone is distilled with conc. sulphuric acid, 1, 3, 5-trimethylbenzene (or mesitylene) is obtained.
In this reaction, 3 molecules of acetone undergo aldol condensation reaction. Thus, compound X is 1, 3, 5-trimethylbenzene.