watchful

警觉的、警戒的、戒备的

The guard stayed watchful throughout the long night shift.

警卫在漫长的夜班中始终保持警觉。

留心的、注意的、看顾的

The children played under the watchful eye of their teacher.

孩子们在老师的注视下玩耍。

密切注意、留意、盯著

Please keep a watchful eye on the soup while I'm out.

我出去的时候，请帮我留意一下汤。