Which three expressions use proper syntax?

Which three expressions use proper syntax?

A.
If (incidents.assgn_acct_id IS NULL, ‘Not Assigned’, 0)

B.
Date_diff(incidents.closed, incidents.created)

C.
If(incidents.assign_group_id = 100460, ‘With Support’, ‘Not with Suport’)

D.
Sum(if(incidents.status_id < > 2, 1, 0))

E.
Avg(incidents.c&times_opened)