国家开放大学 / 综合英语（1）
正确率：100%
The first balls were probably made of _ _ _ _ _ _ _ _ _ .
a.animal skins stuffed with rocks
b.grass or leaves tied with vines
c.hides stuffed with hay or feathers
d.twists of hay
a.animal skins stuffed with rocks
b.grass or leaves tied with vines
c.hides stuffed with hay or feathers
d.twists of hay
参考答案：
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