Select the most appropriate meaning of the underlined idiom in the given sentence.

He runs for two hours at a stretch to build his stamina.

continuously

The answer is >!continuously.!<

The idiom "at a stretch" means without stopping. In the sentence, "He runs for two hours at a stretch to build his stamina," it means that he runs for two hours without stopping. This is because he is trying to build his stamina, which is the ability to do something for a long time without getting tired.

The other options are not correct.

• "Painfully" means in a way that causes pain. This is not the case in the sentence, as the runner is not in pain.
• "Easily" means without difficulty. This is not the case in the sentence, as running for two hours is not easy.
• "Comfortably" means in a way that is not uncomfortable. This is not the case in the sentence, as running for two hours can be uncomfortable.