下列生态系统中,自我调节能力最强的是 [ ]
A.北极苔原
B.热带雨林
C.人工草场
D.农田
答案:B
---Waiter, _____
---Wait a minute, sir. That’s 80 dollars altogether.
A.how much did we eat?
B.Would you please charge me?
C.May I have the bill, please?
D.Would you take the money?
履带式摊铺机对路基的平整度不太敏感,能有效地保证摊铺平整度。