What is true of using group functions on columns that contain NULL values?
A.
Group functions on columns returning dates include NULL values.
B.
Group functions on columns returning numbers include NULL values
C.
Group functions on columns ignore NULL values.
D.
Group functions on columns cannot be accurately used on columns that contain NULL
values.
“All aggregate functions except COUNT(*), GROUPING, and GROUPING_ID ignore nulls.”
https://docs.oracle.com/database/121/SQLRF/functions003.htm#SQLRF20035
http://www.aiotestking.com/oracle/what-is-true-of-using-group-functions-on-columns-that-contain-null-values/