Question

lin missed the boat and did not know how to do the project. the directions the teacher gave him went ______. out of the blue up in the air in one ear and out the other

Explanation:

We need to choose the idiom that fits the context. "Out of the blue" means unexpected, which doesn't fit here. "Up in the air" means undecided, also not fitting. "In one ear and out the other" means someone didn't pay attention to what was said, which matches Lin not knowing how to do the project because he didn't absorb the teacher's directions.

Answer:

in one ear and out the other