Gwen agrees to participate in a six$-$month weight loss challenge sponsored by her employer as part of her employer's commitment to increase mental and physical health among its employees. Gwen is not required to participate in the challenge but must undergo a medical examination, weight check, and blood pressure screening if she wants to win the $$700$ cash prize. The challenge and its requirements:

a$.$ violate the ADA as a post$-$hire medical examinations that are not job related consistent with a business necessity

b$.$ violate the ADA if Gwen's weight is a direct threat to her own safety or the safety of others.

c$.$ do not violate the ADA because they fall in the 'unrestricted' zone that exists following a conditional offer of employment

d$.$ do not violate the ADA