Which of the following statements regarding network maintenance work are true? (Multiple Choice)
A . For device software maintenance, onsite operations are allowed but only remote operations are recommended.
B . The device software running is closely related to services running on the device.
C . The external environment where hardware runs does not need special attention.
D . For device environment maintenance, maintenance personnel need to go to the site or even use some professional tools for observation and measurement.
Answer: BD