对膨胀用二氧化碳含磷量的限制要求为总磷不高于5PPM。
参考答案：错
It said the country's confirmed H7N9 cases were isolated and there has been no______ of human-to-human transmission.
A．mark
B．symbol
C．sign
D．signal
牛顿是（）的单位。
A.轴力
B.应力
C.扭矩
D.弯矩
