Which skeletal disorder involves a gradual deterioration of joint cartilage, leading to joint pain and stiffness?

So i have a lot of answers answered but it says i still need to answer more questions. why is it doing that? how many questions need to be answered?

Vitamin d is unique in that it has a site of synthesis that is different from the location of action, so it is considered to be a click the answer you think is right. enzyme. lipase. nonessential nutrient. hormone?

True or false? the usa has one of the safest food supplies in the world