Is language an abstract or a concrete noun?

It is an abstract noun because you can touch it

As the boys sleep, military airplanes battle fiercely above the island. none of the boys sees the explosions and flashes in the clouds because the twins sam and eric, who were supposed to watch the signal fire, have fallen asleep. during the battle, a parachutist drifts down from the sky onto the island, dead.

The answer is d. prior knowledge. she breaks it into parts in order to figure out what other words have the same parts to the word and put the meanings together.