外管道若在检修时候用火，需要用氮气进行顶液化气的操作。
参考答案：错
解析：外管道若在检修时候用火，需要用水进行顶液化气的操作。
— Where is Toronto?
— ________.[ ]
A. It's in the United States
B. It's in Russia
C. It's in Canada
D. It's in Singapore
T-P-N动物群与E-E-L动物群T、P、N动物群
