供暖系统供水、供汽干管的末端和回水干管始端的管径不宜小于( )。
A. DN20
B. DN25
C. DN32
DN40
Listen to the dialogues and choose the best answer for each question.Dialogue One question 1
A. Leisure sports shoes.
B. Leisure sports activities.
C. Leisure sports facilities.
D. Leisure sports people.
question 2
A. 505 men.
B. 500 women.
C. 505 men and women.
D. 500 men and women.
question3
A. 27 to 35.
B. 36 to 45.
C. 18 to 26.
D. 46 to 60.