What does the American Customer Satisfaction Index provide?

a$.$

A test that companies can take to obtain a $5-$star system rating to prove their customer satisfaction level.

b$.$

A government organized website where customers can publish their feedback about the top $200$ American companies.

c$.$

A customer satisfaction database from which managers can gain important insights. The database can be used to classify companies according to their customer satisfaction level.

d$.$

It is compared to the S&P Index; it provides a sound investment opportunity in companies with superior customer satisfaction