What should a social worker do when developing informed consent for measuring the effectiveness of services offered to chronically mentally ill clients at a community clinic, considering the clients' varying levels of competency on a daily basis?

A) Implement a one-size-fits-all informed consent form to maintain consistency.
B) Assess the clients' competency at the time of the study and obtain informed consent accordingly.
C) Exclude clients with fluctuating competency from the study to ensure validity.
D) Rely on proxy consent from family members or legal guardians to mitigate competency concerns.