Which of the following describe(s) cyclin-dependent kinase (cdk)

The right answer for the question that is being asked and shown above is that: "e) b and c." Cdk is present throughout the cell cycle; Cdk is an enzyme that attaches phosphate groups to other proteins 

These are the following choices:
a)cdk is inactive in the presence of cyclin 
b) cdk is present throughout the cell cycle 
c) cdk is an enzyme that attaches phosphate groups to other proteins 
d) a and b 
e) b and c