This is the second time that the top 10 list of popular novels _____ published by this magazine. [ ]

A. has been

B. are

C. is

D. have been

保险保障以( )为基础，主要来源于投保人交纳的保险费，其形成也有科学的数理依据，而且国家对保险公司有最低偿付能力标准的规定。

A．金融产品
B．保险基金
C．风险保障
D．大数法则