有一批抗锈病(显性性状)小麦种子，要确定这些种子是否纯种，正确且简便的方法是(　　)

News 1
Yuan Longping, the father of hybrid rice, won the World Food Prize on Monday. Yuan developed the world's first popular and widely known hybrid rice. Hybrid rice plants can make more rice than regular ones.
News 2
Have you ever got angry at books that are full of mistakes? Don't worry, things will get better soon. Last week, China started checking textbooks, dictionaries and children's books all over the country. The government said the results of the check would come out at the end of June.
News 3
People will see a new "star" in the sky soon. China plants to send a satellite into space by December 2006.It will stay in space for one year. It will go around the moon and take pictures. It must be very expensive, right? That's for sure,1.4 billion yuan!
News 4
Have you ever thought of being able to fly around the world in a few hours? One day, maybe you can. Last Saturday, the American X-43A airplane made its first flight. It reached a speed of 8,000 kilometers per hour. This makes it the fastest plane in the world.X-43A is only three to four meters long, but it's very heavy. It weighs 1,270 kilograms.

已知M,N为集合I的非空真子集，且M，N不相等，若$N\cap C_{I}M=\varnothing$则$M\cup N=$（    ）