Pick the pair that is incorrectly matched

The correct option is Abies – wood tar, wood gas.

Let us examine the options step-by-step to understand why this pair is incorrectly matched:
1. Cycas – coralloid roots: This is a correct match. Cycas has specialized roots called coralloid roots, which form a symbiotic association with nitrogen-fixing cyanobacteria like Anabaena and Nostoc.
2. Pinus – Mycorrhizal roots: This is a correct match. Pinus roots form an obligate symbiotic association with fungi (mycorrhizae) to assist in the absorption of water and minerals from the soil.
3. Abies – wood tar, wood gas: This is an incorrectly matched pair. Wood tar and wood gas are typically obtained as by-products from the destructive distillation of wood from trees like Pinus (pine) or other hardwoods, not from Abies (fir). Abies is primarily known for producing products like Canada balsam (specifically from Abies balsamea) and resin, rather than wood tar and wood gas.
4. Sequoia – Red wood tree: This is a correct match. Sequoia sempervirens is commonly known as the giant redwood tree and is one of the tallest tree species in the world.

Therefore, the pair "Abies – wood tar, wood gas" is the incorrectly matched one.