数一数左图中一共有____条线段．

已知 $\left|\overrightarrow{a}\right|=3$ ， $\left|\overrightarrow{b}\right|=2$ ，若 $\overrightarrow{a}\cdot \overrightarrow{b}=-3$ ，那么向量 $\overrightarrow{a},\overrightarrow{b}$ 的夹角等于（   ）

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下面画一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

    I woke up lately yesterday because my alarm clock didn't ring. With no time for the breakfast, I rushed out of my house. I had intended to catch the 7:30 subway, and I didn't make it. Have a little time left, I take a taxi instead. I arrived at the school only find, with great sadness mixed with some relief, that the school where should have been full of students was empty. It was Saturday. However, our ill luck showed no sign of coming at an end. When I returned home, I found myself lock out. I had left my key at home. Just my luck.