Brain Buster

Here are the question and answers for this weeks and last weeks brain busters ...

a person was building a house, and then it fell
down, he did not get hurt nor get mad,on the count on, he knew it was going to fall and he did not expect any one to live in it.what happened? The person was using a deck of cards... 

Here is this week's ---  

If you speak correctly, you will be able to answer the following question. Which is correct?
"The yolk of an egg is white"
or
"The yolk of an egg are white"?