下图是肝脏横切正常超声图像，请回答箭头所指部位的解剖名称（）
A.门静脉主干
B.第二肝门
C.第一肝门
D.肝静脉
参考答案：C
根据要求改写句子和填空。
1. We had a maths exam yesterday. (对划线部分提问)
_____ _____ you _____ yesterday?
2. I want to get another piece of cake. (保持原意，改写句子)
I _____ ______ to _____ _____ _____ piece of cake.
3. The snow was very heavy yesterday. (改为同义句)
_____ _____ very _____ yesterday.
4. He'll buy some school things tomorrow. (改为否定句)
He ______ ______ ______ school things tomorrow.
科普是（），是社会主义物质文明和精神文明建设的重要内容。
A、商业行为
B、公益事业
C、社会福利事业
