Which is the best bidding option for an advertiser who wants to drive more clicks from mobile devices?
- Mobile bid adjustments
- Target return on ad spend (ROAS)
- Target search page location flexible bidding strategy
- Cost-per-acquisition (CPA)
Use device bid adjustments to show your ad more or less frequently for searches that occur on specific devices: computers, tablets or mobile devices.
Just as with desktop AdWords campaigns, mobile campaigns use bidding and targeting to determine where and when your ads show up. A click may be worth more to you if it comes from a mobile device or a specific location, or at a certain time of day. By setting bid adjustments, you can increase or decrease your bids to gain more control over when and where your ad is shown.
Read more here: https://support.google.com/partners/answer/6209121?hl=en