海关诸多业务制度中最基本、最核心的一项业务是( )。
A．保税制度
B．关税制度
C．监管制度
D．稽查制度
参考答案：C
Mary had taken _____ to see that her guests had everything that they could possibly want.
A．efforts
B．pains
C．attempts
D．endeavors
请问历史上著名的“八王之乱”发生于哪个朝代？
