With the Self-Explicated Model, the first screen in the Conjoint Phase, is the Level Elimination Page. This allows the respondents to eliminate some levels for some attributes which they would never ever consider.

You can control which attributes this "Elimination" is applicable for.

If you do not want your respondents to un-select Levels from a particular Feature then check this box.

NOTE: If all the Features have this option then the Level Elimination Page is not displayed at all to the respondent.