<p>They’ll see your grades when you apply, but they’re self reported during application time. That means you fill in what schools you went to, classes, grades, etc. After you get in they tell you to send official transcripts, and you’re in trouble if it doesn’t match what you told them on the application.</p>
<p>I wouldn’t bother putting an explanation for the grades. First of all, the reason doesn’t carry a whole lot of weight (I don’t like my sister and I didn’t care about school), if it was a more tangible problem (like a family death mid-semester) then it might make sense… but in this case, I wouldn’t mention it. Second, the classes you got B’s in aren’t really related to your major, so a not-great grade in them isn’t quite as big a deal as it would be otherwise. I wouldn’t suggest explaining a “bad” grade unless it’s actually bad.</p>