Which of the following conditions will make a relation that is in first normal form to be in second normal form Ⅰ. every non-key attribute is functionally dependent on the full set of primary key attributes. Ⅱ. no non-key attributes exist in the relation. Ⅲ. the primary key consists of only one attribute.
A．Ⅰ only
B．Ⅰ and Ⅱ only
C．Ⅰ and Ⅲ only
D．any of them