家鸽的体表被覆________,家鸽的飞行器官是____。
羽毛 翼
— How much are they?
—Sorry, they're not _____ sale. [ ]
A. in
B. on
C. for
有关缺铁性贫血,正确的说法有()
A.是小儿常见疾病
B.多见于学龄期儿童
C.影响智力
D.身体抵抗力低下
E.影响儿童的生长发育