Which of the following values cannot be stored in acharacter column defined as the primary key of a table?

Which of the following values cannot be stored in acharacter column defined as the primary key of a table?

A.
null

B.
‘0’

C.
‘null’

D.
”

Explanation:
A primary key must be defined as NOT NULL. For a character column, any value, even a space, or lack ofa
space, is a valid value. So the strings ”, ‘null’,and ‘0’ are valid strings and would be accepted asinput into a
column that is a primary key. The value null is notacceptable.