雷达是依照某种动物的回声定位原理发明的,这种动物是( )
A:蝙蝠
B:海豚
C:长颈鹿
D:乌龟
金属钒被誉为“合金的维生素”。五氧化二钒(V2O5)中钒元素的化合价为 ( )
What kind of structure is the sentence “The girl showed her classmates some of her family photos.”?