应用于医学领域最早的辐射能源是()
A．β线
B．γ线
C．X线
D．钴
E．镭
参考答案：C
–Bruce, I really appreciate your handwriting.
- _______. .
A．I practice every day
B．Thank you very much
C．No, I don’t think so
D．Well, it’s not good enough
我国人口的突出特点是 [ ]
A．城镇人口比重大，农村人口比重小
B．人口分布均匀，东西差距不大
C．人口基数大
D．人口增长快
- _______. .