阅读理解

    Hello, I'm Bob. Look! This is a book. It's my English book. That is a black eraser. It's Mike's eraser. My eraser is black. It's in my pencil box. Oh! What's that? It's a dictionary. It's Tom's dictionary. Are the rulers Tom's? No, they aren't. They're Jenny's.

铁有三种常见的氧化物：FeO、Fe₂O₃、Fe₃O₄．现有某铁的氧化物样品，已知其中铁元素与氧元素的质量比是21：8，关于该样品的说法正确的是（   ）

下面图形“躺下”“倒立”“趴下”是由“原图”变化成的，说一说分别是由原图按什么方向旋转多少度变换而成的？

Some sports that were part of the Olympics in the past have been removed to __________  new sports which are more popular.