We could see nothing because the lights suddenly            . [ ]

A. went on

B. went over

C. went down

D. went out

甲向乙借款500万元，丙提供了保证担保，丁提供了抵押担保。请根据民法原理、合同法、担保法回答下列问题：

设甲、乙之间的借款合同为有效合同，甲到期无力还款，乙要求丙承担保证责任，丙主张物保优于人保，其主张是否符合法律规定为什么