Answer: B. The squirrel
Step-by-step explanation:
Although the fish is mentioned it only describes that it is circling laps around its bowl, causing no reaction in Milo, but when the squirrel is mentioned to be running from here to there, it says Milo wonders when he would be able to do the same, that is, stop being trapped. The lunch was an interruption and the clock is only mentioned to be ticking.