骨肉瘤的主要血清学化验是：（）
A．酸性磷酸酶活性降低
B． 酸性磷酸酶活性增高
C．碱性磷酸酶活性降低
D．碱性磷酸酶活性增高
参考答案：D
—I had a great time in the summer holidays.We went scuba－diving in Hawaii.
—Wow！________
A．I'm going to Hawaii，too.
B．How generous you are!
C．That sounds really cool!
D．Enjoy yourself!
若工件以内圆孔表面用定位销定位，那么最多能被消除（）自由度。
A.一个
B.二个
C.三个
D.四个
