?!

I happen to notice that every time I log in to facebook there is this ad for painless underarm hair remover on the side of the page.

According to my teacher, the ads are displayed based on your personal information to reach their target markets or whatever.

So..... HOW DO THEY KNOW THAT I AM SECRETLY OBSESSED WITH REMOVING MY BODILY HAIR?

I didn't even like a page like 'feeling good when armpit is clean' or add 'removing armpit hair' under my interests!