明代皇帝的印玺根据不同用途，分为（）
A.十二种
B.十八种
C.二十种
D.二十四种
参考答案：D
---The president _____ by his doctor today that his cancer has come back.
A．informs
B．has informed
C．has been informed
D．is being informed
CMYK模式中共有几个单独的颜色通道（）
A、1个
B、2个
C、3个
D、4个
