下面对土基的加固措施中属于排水固结方法的是（）。

A、开挖换填法

B、砂桩法

C、强夯法

D、粉喷桩加固法

I’m very grateful to Professor Smith, without __________ help I would have never have got this far.

A．who

B．whose

C．whom

D．which