Humans obtain more than 20% information through hearing. Sound perceptible to human ears is a mechanical wave with frequencies within the range ()of Hz.
Answer : C
Color rendering index is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with a standard light source. A smaller value indicates a more faithful color. ( )
Answer : B
A GK sends a/an ( ) message to an upper-level GK for address resolution request.
Answer : D
The three HD display modes provided by the HD video terminal are ( ). (Select 3 answers)
Answer : A, B, D
() is added into the SIP in June, 2002, which is the core standard of the SIP.
Answer : C
The address book file exported from the MCU web interface is in()format.
Answer : A
In video firewall mode, the endpoint connected to the GEO port can call the endpoint connected to the GE1 port by IP address.()
Answer : B