The Following Statements Refer to Potential Limitations of A/B Testing

Multiple Choice

The following statements refer to potential limitations of A/B testing.
I.When single changes are instituted sequentially,A/B testing takes a significant amount of time in order to continuously test and compare modified ads to the current
"best" ad.
II.When multiple changes are made all at once,it is impossible to say which specific
Changes affected the outcome.
Which,if any,of these statements is (are) true?

A) I only
B) II only
C) I and II are both true
D) Neither I nor II are true