I have a lot of interesting topics to discuss with you. Will you come to me after school ______?

A．when you are very convenient

B．when it is convenient to you

C．in the convenience of you

D．when it is convenient by you

债务转让，自( )时发生效力。

A．债务人与受让人达成转让协议

B．债务人与受让人达成转让协议，并通知债权人

C．债务人与受让人达成转让协议，第三人提供担保

D．债务人与受让人达成转让协议，经债权人同意