回收率是指精矿中某金属的质量与原矿中该金属质量的百分数，用“γ”表示。

下列溶液中各微粒的浓度关系一定正确的是[ ]

A.物质的量浓度相同的4种溶液①CH₃COONa②NaNO₃③Na₂CO₃ ④NaOH，pH的大小顺序是：

④>③>①>②

B.在Na₂CO₃和NaHCO₃的混合溶液中：c(Na⁺)+c(H⁺)=c(HCO₃^-)+c(OH^-)+c(CO₃^2-)

C.25℃时，pH=10的CH₃COONa溶液与pH=10的氨水中，由水电离出的c(OH^-)之比为1：1

D.某酸性溶液中只含NH₄⁺、Cl^-、H⁺、OH^-四种离子，溶液中一定存在：c(Cl^-)>c(NH₄⁺)>c(H⁺)>c(OH^-)

《城市房地产抵押管理办法》规定：房地产当事人应在抵押合同签订后( )日内，到房地产所在地房地产管理部门办理房地产抵押登记。

A．7

B．10

C．15

D．30

氯气遇呼吸道黏膜表面水分生成何物而产生局部刺激和腐蚀作用

A．盐酸
B．次氯酸
C．次氯酸和盐酸
D．高氯酸
E．高氯酸和盐酸

Time was running out, and Mark Dickinson wasn't sure whether he'd get to see his dying 2－year－old grandson one last time. A long line at Los Angeles International Airport's security checkpoint had kept him from getting to his gate on time.

His grandson Caden would be taken off life support in a matter of hours in Denver, Colorado, with or without his grandfather's presence, according to CNN affiliate KABC.

“I was kind of panicking because I was running late, and I really thought I wasn't going to make the flight，” Dickinson told KABC.

That's when a pilot from Southwest Airlines stepped up and held the flight at the gate until Dickinson arrived. The pilot was standing by the air bridge waiting for him when Dickinson arrived in socks, so rushed that he just grabbed his shoes at security and ran through the terminal.

“I told him, ‘Thank you so much. I can't tell you how much I appreciated that.’ And he said, ‘No problem. They can't leave without me anyway，’”Dickinson told KABC.

Authorities say Dickinson's grandson, Caden Rodgers, suffered a head injury after his mother's boyfriend threw him across the room. The boyfriend reportedly told police he was drunk and high on marijuana(大麻) at the time. The child later died and the boyfriend has been charged with first－degree murder, according to the Aurora Sentinel.

Thanks to the pilot, Dickinson made it to Colorado in time to say goodbye to his grandson. Most airlines would punish any staff member who holds up a flight, according to consumer advocate Christopher Elliott, who broke the story of the sympathetic pilot on his blog. However, a Southwest spokeswoman said the pilot's actions were praiseworthy.

“You can't hold a plane for every late customer, but I think we would all agree that these were extenuating(可以原谅的) circumstances and the pilot absolutely made the right decision，” Southwest spokeswoman Marilee McInnis said. “I don't think you could ask for a better example of great service for our customers.”

小题1:According to the passage, which is the correct order of the following events?

a. The pilot held the plane for Dickinson.

b. People read the story of the pilot on the Internet.

c. Caden suffered a head injury.

d. Dickinson was waiting in line at the security checking point.

d. Marilee McInnis praised the pilot's actions.

A．d，c，a，b，e

B．c，a，d，b，e

C．c，d，a，b，e

D．d，a，b，c，e小题2:Which of the following statements is true according to the passage?

A．The security staff prohibited Dickinson from getting to his gate on time.

B．The plane couldn't leave without Dickinson according to the regulations.

C．Dickinson made it to see his grandson one last time.

D．Christopher Elliott holds the view that all the airlines should advocate similar actions.小题3:What can we infer from the passage?

A．The boyfriend of Caden's mother hates him very much.

B．The boyfriend has been accused of first－degree murder.

C．Many pilots enjoy writing blog.

D．Dickinson had to take off his shoes at the security cheekpoint.小题4:In writing this passage, the author mainly tells us a story about ________．

A．an unlucky man from Los Angeles making his flight

B．a poor boy being killed by his mother's boyfriend

C．Southwest Airlines' decision not to punish a pilot who held up the flight

D．a pilot holding the flight for a man going to see his dying grandson

民族乐派是在什么样的历史背景下产生的？欧洲不同国家和地区的民族乐派主要有哪些？他们在艺术内容和表现形式上的共同特点主要是什么？