s. alert and fully informed
a. 聪明的, 有知识的
1. She is very knowledgeable about history.
她对历史非常了解。
2. It's helpful to have a knowledgeable friend when studying.
在学习时，有一个知识渊博的朋友是很有帮助的。
3. The professor gave a knowledgeable lecture on science.
教授进行了一个关于科学的知识丰富的讲座。