—Is your brother at home?

—No. He ________ the library. He hasn’t come back yet.

A．was going to

B．has been to

C．has gone to

D．goes to

应承包人要求，发包人提交的保证履行合同中约定的工程款支付义务的担保称为( )。

A．履约担保

B．预付款担保

C．投标担保

D．支付担保