Research which requires filling in a questionnaire just once generally does not fall under the scope of the Medical Research Involving Human Subjects Act (WMO).
However, if you plan on asking the research subjects questions which are detailed, burdensome, or are intimate, for example of a sexual or psychological nature? Or will it take the research subject a lot of time to fill in the questionnaire? Then the research may fall under the scope of the WMO.
When in doubt contact your MREC. More information on the review of WMO research can be found at Primary submission to the review committee.