n.警戒；机敏
The other half of the brain stays awake at a low level of alertness. 另一半大脑在低水平警戒状态下保持清醒。
They also increase alertness and energy. 它们也能提高机敏性和精力。
Without Alertness I'll be stupid. 没有机敏那是愚蠢。
