Why should you only A/B test 1 element at a time? (Select the correct answer.)

A/B testing works best when you change only one element at a time (like a subject line or CTA or image). That way, if performance improves or drops, you can clearly identify what caused the difference. Testing multiple elements at once makes results ambiguous—you won’t know which change drove the outcome. Speed and traffic efficiency aren’t the main reasons; clarity and accuracy are.