肠套叠腹部B超在套叠部位横断扫描可见______或______图像，纵断扫描可见“______”。
参考答案：同心圆；靶状肿块图像；“套筒征”
用括号内所给词的适当形式填空。
1. My _____ (parent) are at home.
2. I like eating _____ (they).
3. _____ (her) is my sister Gina.
4. She is my _____ (mother) friend.
5. Thanks for_____ (help) me.
6. This is _____ (you) class.
在1～1000这一千个自然数中，共有 ______个数码7．
