有的学者认为，对偶婚制大约出现于我国的（）时期。
参考答案：仰韶文化
These story books for children are awfully written. They are _____ interesting _____ exciting. [ ]
A. either; or
B. neither; nor
C. both; and
D. not only; but also
具有消肿生肌功效的活血祛瘀药是（）
A.乳香、没药
B.三棱、莪术
C.煅石膏、牡丹皮
D.白芷、丹参
E.桃仁、红花
