activity book 复数是神马?

activity book 复数是神马? book是神马意思 activity是什么意思activity book friend的复数是神马? chicken的复数是神马 activity book怎么读 activity的复数形式 activity 复数 英语 activity（复数） activity的复数 It was one of the _____（activity） of the“school Open Day”activity是用单数还是复数? 英语语法里的“单数”、“复数”,是神马意思啊? take a book,leave a book 是神马意思是《英语街》的 Whose activity book is that?(同义句) The most exciting activity in this book he geave a book to you是神马结构he gave a book to you here are the result of the student activity survey at Green HighSchool为什么句中的activity不用复数形式,这本来是一道完型填空,填activity的真确形式,请大家说明原因? book的复数形式