Could you please tell me ____?A.how I can solve the problem B.how I could solve the problem

题目

Could you please tell me ____?A.how I can solve the problem B.how I could solve the problem
我知道选B,不清楚为什么.
还有一道：
I'm waiting for my daughter.the train ____she is traveling must be late.
A.which B.that C.on which D.in that
不好意思，第一题选A，我打错了

答案

A.how I can solve the problem 选A的.Could you please tell me ____? 句中Could表示委婉语气,不表示时态的.
C.on which