watchful

警覺的、警戒的、戒備的

The guard stayed watchful throughout the long night shift.

警衛在漫長的夜班中始終保持警覺。

留心的、注意的、看顧的

The children played under the watchful eye of their teacher.

孩子們在老師的注視下玩耍。

密切注意、留意、盯著

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

我出去的時候，請幫我留意一下湯。