Which of the following statements describes a key difference between CDC25 and CDK1, which is the catalytically active subunit of the CycB1/CDK1 complex?
a) CDC25 is a kinase, while CDK1 is a phosphatase.
b) CDC25 is a phosphatase, while CDK1 is a kinase.
c) Both are kinases.
d) Both are phosphatases.