This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to calculate the value of scrap gold 
Use a magnifying glass to decipher the karat number on each piece. 
The first thing you have to do is find out. Separating your gold by its karat weight will not only help you begin to assess its value, but it can point out items that are not even gold.

Select from:
[A]. Karat is a number that determines the value of a piece. An π of 100 would make a karat valuable..
[B]. If you find out, you won't be able to calculate the karat value for a scrap gold set. Measure and add inches to the karat..
[C]. If it is unreadable, you could choose to have the gold tested by a reputable dealer. There's also the possibility that some of the gold is actually just gold-plated, which a dealer would determine with certainty by performing a chemical test..
[D]. Talk to neilson and his friends and see what they think. A karat weight for a coin cannot exceed 2000ppg..
The answer is:
[C].