Ad preference may NOT be used to change keyword bids in Google Ads.
- time of day
- ad preference
The correct answer is: ad preference
Explanation: Ad preference doesn’t come under the bid adjustment. Bid adjustments allow you to show your ads more or less frequently based on where, when, and how people search. For example, sometimes a click is worth more to you if it comes from a smartphone, at a certain time of day, or from a specific location.
In other words, ad preference is called Ad personalization. This Ad preference criterion can never be used to change keyword bid. Ad preference is managed by users. In the Ads preference or personalization setting, users can personalize their Google ad experience by managing the information Google uses to show you ads and making the ads you see more useful to you.
Read more here: https://support.google.com/adwords/answer/2732132