答案：B

题目分析：句意：昆明是一个美丽的城市，那里一年四季都可以见到花草树木。分析语境可知where flowers

and green grass and trees are seen all year round为定语从句，先行词为a beautiful city，先行词在定语从句中充

当地点状语，故用where引导。故选B。