You are doing your homework .（用I做主语改写句子） They are making a cake.（改为一般疑问句）Tom often speaks Chines.（改为现在进行时）Kitty and Ben have lunch at about twelve.(改为现在进行时)

Tom is speaking chinese.
Kitty and Ben are having lunch now.

1、You are doing your homework. 改为 I am doing my homework.
2、They are making a cake . 改为 Are they making a cake?
3、Tom often speaks Chinese. 改为 Tom is speaking Chinese. (另外，更正一下，Chinese而不是Chines)
4、Kitty and Ben have lunch at about twelve. 改为 Kitty and Ben are having lunch now.

You are doing your homework.改为:I am doing my homework.
They are making a cake.改为：Are they making a cake?
Tom often speaks Chinese.改为：Tom is speaking Chinese (now).
Kitty and Ben have lunch at about twelve.改为：Kitty and Ben are having lunch (now).