糖尿病患者，尤其病程在10年以上者，其腿部病变发病率超过（）
A.30％
B.40％
C.50％
D.60％
E.70％
参考答案：C
Every year _______ of trees are planted on the hills to protect the environment.[ ]
A. a thousand
B. thousands
C. thousand
The major components which determine the length of a catenary in a deployed anchor cable are water depth，cable weight，and（）.
A.cable tension
B.water temperature
C.bottom conditions
D.water density
