题干
______ was most shocking about the tornadoes in America was that they threatened six states and killed more than 100 persons.
A：That
B：Which
C：Why
D：What
答案(点此获取答案解析）
D
，
为其前
项和，定义
为A的“凯森和”，如果有99项的数列
的“凯森和”为1000，则有100项的数列
的“凯森和”为（ ）
