机械除草的限制因素有哪些？
参考答案：
（1）机械除草受环境条件制约，无选择性；
（2）作物含水量；
（3）作物生育期。
The nurse is teaching the parents of a school-age child. Which teaching topic should take priority（）
A. Preventing accidents.
B. Keeping a night light on to allay fears.
C. Explaining normalcy of fears about body integrity.
D. Encouraging the child to dress without help.
三星级饭店属于（）水平的饭店。
A.高等
B.低等
C.中等
D.特等
