1 . The greatest historical treasure of all is London with its museums, art c_______（收藏品）, theatres, parks and buildings.

2 . The Art Gallery has the world’s largest c________of sculptures by Henry Moore. (根据首字母提示完成句子)

3 . The painting comes from his private________(收藏).(根据汉语提示单词拼写)

4 . With their patience and efforts, Chris and Tim successfully developed a ____ of artificial breeding (人工繁殖）and natural reproduction.

A．collection

B．combination

C．system

D．strategy