例句：

　　The drug improved mental alertness.

　　這種藥物提高了大腦的靈敏度。

　　That purpose is alertness.

　　這個目的就是警惕。

　　They also increase alertness and energy.

　　它們也能提高機敏性和精力。

　　It made some evolutionary sense, that state of alertness.

　　那種警覺的狀態(tài)會形成某種進化感。

　　Research has shown that the lavender scent increases alertness.

　　研究表明薰衣草香味會提高人的警惕性。