What is the main difference between the CAPM and the APT?

A$)$ The CAPM assumes that only one systematic risk factor affects asset returns, while the APT allows for multiple systematic risk factors.

B$)$ The APT is a single$-$factor model, while the CAPM is a multi$-$factor model.

C$)$ The CAPM considers both systematic and unsystematic risk, while the APT only considers systematic risk.

D$)$ The APT is a static model, while the CAPM is a dynamic model.