Whenever I met her, _________ was fairly often, she greeted me with a sweet smile.  

A．who

B．which

C．when

D．that

阅读马致远《天净沙·秋思》，回答下列小题：
枯藤老树昏鸦，小桥流水人家，古道西风瘦马。夕阳西下，断肠人在天涯。