Students were told to inhale and exhale in one of four ways: strictly orally;strictly nasally;orally while wearing a nose plug;or just breathe normally.

• 学生们被要求以下列4种方式之一呼吸：完全用口呼吸、完全用鼻呼吸、戴上鼻塞用口呼吸或正常呼吸。