每平方公里铁路长度属于（）。
A、比较相对指标
B、比例相对指标
C、动态相对指标
D、强度相对指标
参考答案：D
He_____ articles for our wall-newspaper these years, and he____ about thirty articles.
A．has written; wrote
B．has been writing; wrote
C．is writing; has been writing
D．has been writing; has written
对急性胰腺炎具有诊断意义的指标是（）
A.血清脂肪酶测定
B.血清钙测定
C.血、尿淀粉酶测定
D.X线检查
E.CT检查
