Early this morning we set the instruments on the table, and now we’re waiting for our teacher.

which words in the sentence are prepositions?

On is the only preposition in this sentence. A preposition shows location, such as, on, over, beside, etc.

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.