甲、乙、丙、丁四支足球队在世界杯预选赛中进球数分别为9，9，x，7，若这组数据的众数和平均数恰好相等，求出其中的x值以及此组数据的标准差．

    My name is Leo. I am eight years old. I am 1 the UK. I like 2 model aeroplanes. I want to be a pilot. I 3 to fly an aeroplane.

    There are six people in my family. My parents are both 4. I have two brothers, John and Jack. They are both students at middle school. John is good at 5. He wants to help people at sea in the future. Jack paints very 6. He wants to be a painter. I have a sister too. Her name is Daisy. She likes 7 and dancing Very much. She 8 to be a singer.

函数 和y=kx+3的图象大致是（   ）

吞噬细胞不参与的是（  ）