红豆红歌曲原唱俞静:that is a pen

that is a pen that is a green pen表语和宾语是否都是pen，其中that是主语？(详细) Is that a pen?Is that a pencil?(合并为一个选择问句) That is a way it is He is now in the pen.He regretted having done that. That is a ___ idea.(填空） This is a heads up that it is coming.中文？ There is the pen as I last time.中为什么用as而不用that或wich? Linda is writing a litter to her pen pal.(改否定句) ( ) ( ) a pen or a pencil?