a big bag of cobs 做主语,谓语动词用单数还是复数?说明理由~

a big bag of cobs 做主语,谓语动词用单数还是复数?说明理由~ A big bag of potatoes,please. Each of them have a big bag 哪里错了 I bet you a big bag of candies是什么意思 Do you ( )a big bag Each of them has a bag and a big red flag.They __ __ a bag and a big red flag. a bag of rice A bag of b_____. a bag of wind a bag of wind This is a big school bag.感叹句 A.new big blue bag B.big new blue bag C.blue big new bag D.big blue new bag.选那个? My brother is so strong that he can carry a big bag of rice的同义句My brother is——to carry a big bag of rice{横线上填什么} He has a big school bag.(根据划线部分提问) Tom has a big bag in his hand.等于tom（）（）a bid bag toilet big bag and David has a big bag in his hand,(保持句意不变） David__ __ a big bag. 请问a type of small bag中的bag为什么不可数?