The Multichoice poll can be configured to allow for two slightly different type of poll.
- Select the Multichoice poll type.
- Enter your question text and choices.
Then (and here's the key bit) take note of the Allowed Selections box.
As a default, this is set to 1 when you add a new poll, meaning your participants can only select one option.
You can increase this if you want to allow participants to select more than one. You can limit people (e.g. pick three), or set it the same as the number of choices (e.g. for a 'select all that apply' type of poll).