Identify the revised sentence that eliminates the pronoun reference problem in the following sentence:
Fred had few ethical principles; they say he worked for whoever offered the highest fee.
a) Fred had few ethical principles; observers say he worked for whoever offered the highest fee.
b) Fred had few ethical principles; this indicates he worked for whoever offered the highest fee.
c) Fred had few ethical principles; some claim he worked for whoever offered the highest fee.
d) Fred had few ethical principles; it is believed he worked for whoever offered the highest fee.
