he promised --- his old friend dueing his stay in tianjina\ seeb\ seeingc\ sawd\ to see请您说明理由好吗?

he promised --- his old friend dueing his stay in tianjin
a\ see
b\ seeing
c\ saw
d\ to see
请您说明理由好吗?

答案是D,
promise to do something 答应做某事
promise (that) 从句 答应...
promise somebody (that) 从句 答应某人...
promise something to somebody 答应给某人...
promise somebody something 答应给某人...