Another study is performed as follows: All patients diagnosed in a particular rheumatology clinic are invited to participate in a study. Those that agree are followed prospectively for many years. Those with lupus are compared to those without lupus with respect to rates of renal failure among patients with lupus.

What type of study design is this?

a)randomized experiment

b)case control study

c)cohort study

d) cross sectional study

e)simple random sample