Which user characteristic may not be used to change keyword bids in adwords?:?

The question above has multiple choices as follows;

a. time of day

b. ad preference

c. location

d. device

The answer is (B) ad preference.

The rest of the choices are able to change keyword bids in adwords apart from ad preference and are among the several types of bid adjustments. You can show ads more or less frequently based on when, where, and how people search.