道床混凝土强度达到设计要求（）以上，放可行驶轨道车或承重。
A.50
B.80
C.70
D.60
参考答案：C
慢性子宫颈炎的类型有：________、________、____________和________。
An analyst does research about asemiannual-pay callable bond. The bond with a face value of $1000 and a coupon rate of 5% is callable in 4 years at 1020. If the bond matures in 7 years and is currently priced as $980, the yield to worst is closest to:（）
A. 3.01%
B. 5.35%
C. 6.02%
