Why is pilot operated check valve used in clamping operation?
A. to reduce leakage in spool valve
B. to avoid decrease in pressure during clamping
C. both a and b
D. none of the above
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Which of the following statements is true, for two pumps used in circuit when initially fast operation is performed to reach a workpiece and feeding operation is done at a slow speed?
A. initially to reach a workpiece, a tool must be connected to a pump of high discharge and low pressure
B. initially to reach a workpiece, a tool must be connected to a pump of low discharge and high pressure
C. for feeding operation low discharge low pressure pump is required
D. none of the above
Which of the following pump system saves more power?
A. single pump
B. double pump
C. single and double pump use same amount of power
D. none of the above
确认httpd服务运行状态的命令为（）。
A. systemctl status httpd
B. systemctl restart httpd
C. systemctl start httpd
D. systemctl enable httpd
网站根目录为（）。
A. /var/www/html
B. /etc/httpd/conf
C. ~/.ssh
D. /ssh
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