is,this,adOII?改为复数句,怎么改?

is,this,adOII?改为复数句,怎么改? This is a book 改为复数句 This is a pear.改为复数句 This is an orange改为复数句 is this your dress?改为复数句 This dress is pretty.(改为复数句) this apple is red改为复数句 this is a tree 改为复数句 This is an orange.改为复数句. IS this your sister?(改为复数句) This is an orange改为复数句 Is this a bus （改为复数句 this is a shirt改为复数句 Is this your photo?改为复数句 This hat is big.改为复数句 this is a watch(改为复数句) This is an orange .[改为复数句] Is this your duck?(改为复数句)