It was my sister __________ first had the idea to cycle along the Mekong River from where it begins ___________ where it ends.

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A．who,to

B．which,till

C．that,till

D．whom,to

It was my sister __________ first had the idea to cycle along the Mekong River from where it begins ___________ where it ends.

［　　］

It was my sister      first had the idea to cycle along the entire Mekong River from ______ it began to where it ends.

A. who; which           B. who; where          C. that; which           D. that; what

It was my sister ________ first had the idea to cycle along the entire Mekong River.

A. who                      B. whom                          C. /                              D. which