问题补充:
They want to develop a kind of dog-friendly food will help dog owners cool down their pets.
A. who
B. what
C. which
D. whether
答案:
A. who
B. what
(答案→)C. which
D. whether
解析:考查定语从句的引导词。句意“他们想研制一种对狗有好处的狗粮,这种狗粮会帮助狗的主人安定他们的宠物。”先行词food指物,排除who;what不能引导定语从句;which指物。故选C。