___the people have become masters of their own country that science can really serve the peopleA only when B it is only when C only when D it is only when

___the people have become masters of their own country that science can really serve the peopleA only when B it is only when C only when D it is only when
___the people have become masters of their own country that science can really serve the people
A only when B it is only when C only when D it is only when

___the people have become masters of their own country that science can really serve the peopleA only when B it is only when C only when D it is only when
b跟d不是一样吗