Some dens are rooms. All rooms are walls. Some walls are bricks, all bricks are plates.

(a) Some plates are walls

(b) Some walls are dens

(c) Some bricks are rooms

(d) Some plates are rooms

(a) and (b) only

Here,

dens ⇒ D, rooms ⇒ R, walls ⇒ W, bricks ⇒ B, plates ⇒ P

According to the question:

The following figure can be made:

From the above figure, only (a) and (b) are correct.