（A）clock and（an）English book are on the computer desk.为什么要用A

（A）clock and（an）English book are on the computer desk.为什么要用A There is a book on the desk,and ____is an English book A.tha 改错An alarm clock and a pen are on the desk . There are two English books and a computer on the desk.改为同义句 There( are )(a book)and (two pens)(on) the desk There are a book and two pens on the desk . _______ clock and a pen __________ on the desk.A.An,is B.A,i ----alarm clock and a CD _______on the desk A An are B A is There ___an English book and a pencil case on desk.A.are B.i There is two English books and a computer on the desk.改为同义句 There( )a computer and two books on the desk.A are B is 改错 Tow keys and a alarm clock are on the desk