依据DL/T869-2004中规定，锅炉受热面管子：外壁错口值不大于10%壁厚，且不大于（）。
A.1mm
B.2mm
C.3mm
参考答案：A
根据反射活动形成的过程，可将反射分为（）和（）两种。
What is the probable relationship between the two speakers [A] Teacher and student. [B] Doctor and patient. [C] Husband and wife.
