there are three rolls of film in my pocket改错要说原因
问题描述：
there are three rolls of film in my pocket改错
要说原因
答
there are three rolls of film（S） in my pocket
我口袋里面有三卷胶卷.
film [ film ] n.电影；薄膜；胶卷；
当胶卷讲时,可数.