How can I limit the number of answer items that can be selected?

Let's assume that you want to create a question where the survey respondents are only allowed to select 3 out of 6 answer items. In order to check the number of selected items, you can use the plausibility check.

Step 1: Create a plausibility (standard check) check on the respective survey page 

Open

Step 2: In order to access the code editor, you have to first enter a random plausibility check definition, otherwise the code editor will not show up (weird I know). 

Open

Step 3: After you have clicked on save, the meta pro editor is visible.

Enter the following code into the editor:

if (( v_43 + v_44 + v_45 + v_46+v_47+v_48) != 3 ) print "Please select 3 items";