Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information A. It is the conventional theory that when people are bored or sleepy, they often experience a drop in blood oxygen levels due to their shallow breathing B. The conventional theory is that people yawn when bored or sleepy because yawning raises blood oxygen levels, which in turn raises alertness C. According to conventional theory, yawning is more likely to occur when people are bored or sleepy than when they are alert and breathing deeply D. Yawning according to the conventional theory, is caused by boredom or lack of sleep and can be avoided through deeper breathing