投资中心是对（）的责任中心。
A、对收入负责
B、对成本负责
C、对收入和成本负责
D、对收入、成本和资金负责
参考答案：D
通常情况下零上10℃用（ ）表示，零下5℃用（ ）表示。
There ______ some paper and three books in his backpack. [ ]
A. isn't
B. aren't
C. is
D. are
