题干
—When will the chat show be on, do you know?
—Yes. The chat show will be on TV _________ 7 p. m. _________ 9 p. m. this evening.
A：from, until
B：between, to
C：from, and
D：between, and
答案(点此获取答案解析）
D
的平均数为h，
的平均数为k, 则把两组数据合并成一组以后，这组样本的平均数为
）