I don't understand what E is trying to say

Hi, This is a necessary assumption question, so we need to find an answer that the author must agree with if their argument is to make sense. The author suggests that human activity is causing a change that happens every seven days, because no natural 7-day cycle could have a large enough effect. E tells us that if a weather pattern with a natural cause occurs every seven days, then the cause itself occurs every seven days. In other words, this is saying that a weekly natural pattern must be caused by something weekly. If E is true, it eliminates the possibility that a 7 day pattern might be caused by something that happens every 14 or 28 days. For example- maybe a low tide happens every 7 days, but the thing that causes the tide (the moon) exists on a 28 day cycle- but still has an influence on something weekly. If this were the case, the author's argument would fall apart- so E must be assumed.