如图,想在河堤两岸搭建一座桥,图中搭建方式中,最短的是PB,理由____.
阅读短文,判断对错。
Look at this photo(照片). This woman is my mother. She is 36. This man is my father. He is 37. This girl is my sister. She is 11. The little boy is me. I am 6. I love them. And they love me very much.
航空航天材料中的重要金属钛(Ti)可以用TiO2与Si反应来制取,反应的化学方程式为TiO2+Si=SiO2+Ti,则该反应属于化学反应基本类型中的( )