I had just taken a bite of my hot dog I heard a familiar voice yelling at me from across the crowded school yard.
A. before
B. while
C. since
D. when
网友回答
A. before
B. while
C. since
(答案→)D. when
解析：考察连词。该句为固定句型，sb had just done sth when sb did sth
意为某人刚做完某事，突然……