Question branching logic allows you to crate path for your respondents. For example if respondent selects answer choice A he will be directed to page 3, if he selects B he will be directed to page 4.
To add question logic :

Single choice question logic redirects you the page indicated in the logic.
Example 1
Survey question logic has been set on page 2. Respondent will be redirected to page 3 if he/she selects answer choice A, or to page 4 if he/she selects answer choice B.

Example 2
Survey question logic has been set on page 2. Page question logic has been set on page 4. Respondent will be redirected to page 3 if he/she selects answer choice A, or to page 5 if he/she selects answer choice B. Page logic on page 4 will redirect respondent to page 7 regardless the answer he/she will provide.

NOTE. You have to divide your survey into pages before you start to design question logic.
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