什么是三级动火范围？
参考答案：
凡属于非固定动火区域，没有明显危险因素的场所，必须进行临时焊割时，都属于三级动火范围。
胚层逆转
The 20th-century poem suggests to something we have been able to find nothing about.
A．alludes
B．avoids
C．alleges
D．alerts
