X and Y are thick, black liquids which can be used for metalling the roads. X…

Refining crude petroleum leaves behind a thick, black, viscous residue called bitumen, which is used as a waterproof binder for surfacing (metalling) roads. When coal is heated to make coke, it releases coal tar as a by-product — also a thick, black liquid, and one that has historically been used to surface roads as well.

Since X is described as petroleum-derived, X must be bitumen. Since Y is described as coal-derived, Y must be coal tar. So X and Y are Bitumen and Coal Tar respectively.

• Coal Tar, Charcoal — coal tar is coal-derived, not petroleum-derived, so it cannot be X; charcoal is obtained by charring wood, not coal, so it cannot be Y either.

• Charcoal, Bitumen — charcoal comes from wood, not petroleum, so it cannot be X; bitumen comes from petroleum, not coal, so it cannot be Y.

• Coal Tar, Bitumen — this pairing swaps the two correct substances: coal tar is the coal-derived one (so it fits Y, not X), and bitumen is the petroleum-derived one (so it fits X, not Y).