Among the choices listed which one pair of fields or column

Among the choices listed, which one pair of fields (or column headings) could not constitute a composite key for the table below?

Solution

A composite key is a combination of two or more columns in a table that can be used to uniquely identify each row in the table when the columns are combined uniqueness is guaranteed, but when it taken individually it does not guarantee uniqueness.

So,if you observer given table, then

for combination: Project, Color_code : no two rows have same value
for combination: Quantity, Color_code : no two rows have same value
for combination: Project, Quantity : no two rows have same value

So, we can use any combination to formulate composite key for above table

ANs: D