What is one reason that it is difficult, although not impossible, to overcome biases or errors in rating employees?

a) Some biases operate on an unconscious basis.
b) Most supervisors are older and do not want to change their methods.
c) The methods being used have been in place for many years and would cost a lot to change.
d) Many companies understand their methods may be less than ideal, but they are afraid of lawsuits if the methods are changed.

A