可以说There is a pen here吗

可以说There is a pen here吗 There is a pen in my pen. 可以说in there ,in here吗? 可以说there is a knock at the door吗 there is a pen.对划线部分a pen提问 there is a pen 对a 提问 there is a pen on the desk? there is a pen in the pencilbox Bob is a boy.Her pen is here.(单句改错) There is a pen and a pencil 还是There are a pen and a pencil there is a pen on the table;那there are pens on the table可以吗? Here is a pen and two pencils on the desk.