a book and a pen is on the desk.对吗,为什么?

a book is {}the pencil and the pen.空里填什么? There is a book and a pen on the table改为复数句 a book and a pen is on the desk.对吗,为什么? There is a book and a pen on the desk.(变为否定句) Three___a pen and four book on the table.a:is b:are There( ) a pen and a book on the tabie . there is a pen ,a towe ,I a toy and a key ring in my book.改错 A book,a pen,a ruler and an eraser___on the desk.请问是填is还是are?要用就进原则吗? I have a book and pen.变成一般疑问句 this is an english book （）that is a pen 填空,有选择,and,too,but,or there is a book and two pen on the table just now.如果不对那填什么? is that your a book?哪里错了This is a pen and that's a ruler?Is this his pencil?哪里错了!求 This is a pencil and a pen还是These are a pencil and a pen There is a pen and a pencil 还是There are a pen and a pencil I can see a book on the desk,a clock（）the book and a pen（）the book a book and pen 有没有这种用法：a book,a pen,...,and a bottle = a book,pen,pencil,cup,and bottle.即省略后面全部的a, This is a pen and ____ is a pencil. there is a key and a book