简述如何预防维生素缺乏。
参考答案：1、膳食品种多样化2、减少烹调加工中损失3、治疗妨碍其吸收的疾病4、各种维生素供应应保持数量平衡。
—Last week American doctors ______ his foot.
—They say Liu Xiang may run ______ after the operation. [ ]
A. operated on; even faster
B. operation on; even fast
C. operated to; much faster
D. operated; more faster
()是我国古代城市规划思想最早形成的时代。
A.西汉
B.东汉
C.战国时代
D.周代
