求教！GWD 17—23

Because visual inspection cannot reliably distinguish certain skin discolorations from skin cancers, dermatologists at clinics have needed to perform tests of skin tissue taken from patients.  At Westville Hospital, dermatological diagnostic costs were reduced by the purchase of a new imaging machine that diagnoses skin cancer in such cases as reliably as the tissue tests do.  Consequently, even though the machine is expensive, a dermatological clinic in Westville is considering buying one to reduce diagnostic costs.

Which of the following would it be most useful for the clinic to establish in order to make its decision?

1. Whether the visits of patients who require diagnosis of skin discolorations tend to be shorter in duration at the clinic than at the hospital
2. Whether the principles on which the machine operates have been known to science for a long time
3. Whether the machine at the clinic would get significantly less heavy use than the machine at the hospital does
4. Whether in certain cases of skin discoloration, visual inspection is sufficient to make a diagnosis of skin cancer
5. Whether hospitals in other parts of the country have purchased such imaging machines

分析求！ THX

我的理解：

大医院很有效，因此问小诊所是不是也要买？

有助判断：在小诊所也一样用的多。因为怀疑小诊所是否有和大医院一样多的病人来看病，所以要问这个情况，才好判断买不买。如果小诊所看病的人少，买来是不会减少诊断费用的，因为少病人来分摊这个费用。