A：sung
B：singing
C：sing
D：to sing
⑴Are these your shoes? ____ A. It's a T-shirt.
⑵What are these ? ____ B. They are keys.
⑶What is this? ____ C. Yes, they are.
⑷Is this your blue shirt? ____ D. It's Jenny's.
⑸Whose sweater is this?____ E. No, it's not.
在一个圆中，圆的周长是直径的____倍，是半径的____倍。
二氧化钛（TiO2）是一种广泛用于光化学反应、太阳能电池的物质。某学生设计了如下实验方案，其中不能反映二氧化钛化学性质的实验是( )
There is old bike under the tree. old bike is Mr. Zhao's.
已知圆的半径是23，则该圆的内接正六边形的面积是（ ）
