Upvote:7
There could be countless other things you haven't mentioned, but if you apply again, don't stay silent when answering a question! They asked about whether or not your friend is accompanying you. You stayed silent. That's a BIG red flag - anyone refusing to answer a question implicitly indicates they have something to hide.
They want to be sure you're a genuine, open tourist with no ulterior motives. Appearing to hide information does not convince them of this.