What are two rules for compacting IPv6 addresses?（）

• A、Every 16 - bit segment segment that consists of all zeroes can be represented with a single colon.
• B、The trailing zeroes in any 16 - bit  segment do not have to be written.
• C、The leading zeroes in any 16 - bit segment do not have to be written.
• D、Any single, continuous string of one or more 16 - bit segments that consists of all zeroes can be represented with a double colon.
• E、The maximum number of times a double colon can replace a 16 - bit segment that consists of all zeroes is two.
• F、Two zeroes in the middle of any 16 -bit segment do not have to be written.