Can you smell two things at once? This experiment comes from the research of two scientists from Rice University. Denise Chen and Wen Zhou have been experimenting with the science of smell, and have made some very interesting discoveries.
To explore that, you will need two things with strong, characteristic smells and, of course, your nose. The idea is to smell a different smell with each nostril (鼻孔). Hold one smell very close to your right nostril, and the other smell very close to your left nostril. Then breathe in and pay close attention to what you smell.
What you should find is that one smell will be very strong. After another sniff (嗅) or two, the first smell will go away, and you will smell the other smell. Keep sniffing, and the first smell will come back. Instead of smelling the two smells evenly (均匀地) mixed, they will work in turns, one after the other.
Why? Chen and Zhou found that your sense of smell acts much like your sense of sight. Hold a book in front of your nose, so that your left eye sees things on the left side of the book, and your right eye sees things on the right side of the book. You will find that your sight works in turns, first on the left side of the book and then on the right side. Notice that you can’t focus your left eye on one object while focusing your right eye on another object. Your brain jumps back and forth (来回地), paying attention to one and then the other. The same thing happens with your nostrils. If they are smelling different smells, your brain pays attention to one and then the other.
29. Which of the following is TRUE about the experiment?
A. B.
.
C. 
D. 
30. Denise Chen and Wen Zhou discovered that ______.
A. our brain focuses on one thing at a time
B. our two nostrils act differently towards the same smell
C. our nose prefers to smell stronger smells
D. our sense of smell is connected with our sense of sight
31. The last paragraph is developed by ______.
A. giving examples B. making a comparison
C. telling a story D. showing the results
32. The main purpose of the text is to ______.
A. report an important event
B. describe a scientific experiment
C. study how the sense of sight works
D. introduce two scientists from Rice University