小儿腹部肿瘤常见的有（）.
A.嗜铬细胞瘤
B.神经母细胞瘤
C.肾母细胞瘤
D.畸胎瘤
E.以上都正确
参考答案：B, C, D
He said that light _______ much faster than sound. [ ]
A. traveled
B. will trave
C. travels
D. is traveling
透检测方法的基本原理是什么？
