单选题Which of the following operating features do displacement pumps bear if they are working under no-cavitation condition?（） (1) output is almost directly proportional to speed (2) they are self-priming (3) they will develop a discharged pressure equal to the resistance to be overcome, irrespective of speedA（1）and（2）B（2）and（3）C（1）and（3）D（1），（2）and（3）
单选题
Which of the following operating features do displacement pumps bear if they are working under no-cavitation condition?（） (1) output is almost directly proportional to speed (2) they are self-priming (3) they will develop a discharged pressure equal to the resistance to be overcome, irrespective of speed
A
（1）and（2）
B
（2）and（3）
C
（1）and（3）
D
（1），（2）and（3）
参考解析
解析：
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