一般发动机在地面工作时，整流罩鱼鳞片应处于什么位置（）.
A.完全关闭
B.完全打开
C.打开1/3
D.打开2/3
参考答案：B
生物的多样性包括生物种类的多样性、______的多样性和______的多样性．保护生物多样性最为有效的措施是______．
Sam is training for the marathon. He drove 12 miles from his home to the Grey Hills Park and then ran 6 miles to Red Rock, retraced his path back for 2 miles, and then ran 3 miles to Rock Creek. If he is then n miles from home, what is the range of possible values for n ？（）
A. 1≤n≤23
B. 3≤n≤21
C. 5≤n≤9
D. 6≤n≤18
E. 9≤n≤15
