This post of Question 21 of a Hong Kong Elementary School Admissions Test has gone viral in China. You have twenty seconds to answer it correctly, if you want to prove that you are smart enough to be a Hong Kong first grader.
Scroll down the page if you want to see how to find the answer.
For the answer, turn your computer screen upside down, or look at the screen while doing a handstand.
(H/t China Smack)