2 . The researchers ________ red balls for blue balls to see if the baby would notice.

A．exchanged

B．substituted

C．replaced

D．alternated

4 . Directions: Complete the following sentences by using the words in the box. Each word can only be used once. Note that there is one word more than you need.

A. compliment               B. emphasis                     C. undergo                     D. obsess E. alternate                     F. perspective               G. supply                     H. issue I. suspect                     J. reverse                            K. proceed

1. He said British troops would stay on in Afghanistan for the time being, but promised increased ________ on training the Afghan military and police to take over responsibility security.
2. Searching through a variety of sources will give them a wider ________ on their subject.
3. Yet his manner made it clear that he was simply stating a fact, not flattering with a ________.
4. I think no matter what diets we follow or what slimming products we ________ ourselves with, at the end of the day there's no magic trick to shape up for the summer.
5. The wedding license bureau had told Cheryl that no one there had the power to ________ an emergency license by phone, but maybe she could try to reach a judge.
6. To survive, he says, companies must ________ a transplant of corporate DNA, and few survive the surgery.
7. A lawyer from the district attorney's office presents a case against the ________.
8. The teacher should encourage the child to ________ as far as he can, and when he is stuck, ask for help.
9. The building projects are behind schedule and construction materials in desperately short ________.
10. While Apple may face enormous competition, the company is known for taking ________ routes.