本题答案为 B.from where .
from where 引导非限制性定语从句,其先行词是以地点名词the window为中心的前面的一句话.意指 from the place wherethe man was standing.
当先行词是以地点名词或者时间名词为中心的一句话时,定语从句由“介词+where”或者“介词+when”.其中,when=which place,when=which time.
当先行词是地点名词或者时间名词,并且,它们作介词宾语在定语从句中作地点或者时间状语时,定语从句由where或者when引导,相当于“介词+which”.
比较：
① He stood at the window,____ he could see what was happening.
A.from where B.from which C.which D.at which、
② The southern states wanted to set up a country of their own,where/in which they would be free to keep black slaves．