打（压）入桩施工，斜桩倾斜度允许偏差为（）%tanθ。
A、10
B、15
C、20
参考答案：B
A stock priced at $100 has a 70 percent probability of moving up and a 30 percent probability of moving down. If it moves up, it increases by a factor of 1.02. If it moves down, it decreases by a factor of 1/1.02. What is the probability that the stock will be $100 after two successive periods（）
A. 9%.
B. 42%.
C. 21%.
传热恶化有（）和（）。
