he is only seven.he can go to school.（合并为一句）He is_____ _____ to go to school.
还有一道数学题,这是《开放做法本源图》,图中a为几?
1
1 1
1 2 1
1 3 3 1
1 4 a 4 1
1 5 10 10 5 1
就是居中排列，不好意思我打错了。