Forcing horizontal format for multiple choice questions on mobile devices

Hi everyone,
I have a set of 2-option multiple choice questions that I want to present on mobile devices only. It is essential that the response options (consisting only of the words YES and NO) are presented horizontally. On mobile devices, however, the default presentation is vertical.
Can anyone help me implement one of these solutions:
1) a way to force users to flip their mobile device horizontally so that the default mode becomes landscape
2) (preferred option) some CSS code to force the presentation of the options in horizontal format, regardless of the orientation of the device.
I've read several threads already but can't seem to find a solution!
Many thanks!