短时记忆的容量是( )。A．无限的B．9个以上的项目C．7±2D．无法测量的

在一个球袋中放有7个红球、3个白球、2个黄球，把球摇匀后摸到（      ）球的可能性最大。

根据下列化学实验事实得出的结论一定正确的是 [ ]

A. 向某无色溶液中先加入氯化钡溶液，生成白色沉淀，再加入足量盐酸，沉淀不溶解

结论：该溶液中一定有SO₄^2-

B. 用洁净的铂丝蘸取某无色溶液在酒精灯上灼烧，透过蓝色钴玻璃火焰呈紫色

结论：该溶液中一定有K⁺

C. 向某无色溶液中加稀盐酸，产生无色无味且能使澄清石灰水变浑浊的气体

结论：溶液中一定有CO₃^2-

D. 向NaCl溶液中滴加AgNO₃溶液产生白色沉淀，继续滴加KI溶液沉淀转化为黄色

结论：Ksp(AgCl)>Ksp(AgI)

Every year, major storms cause many problems around the world. There is nothing people can do to stop these powerful forces of nature. But new techniques are helping scientists to predict how, when, and where big storms will happen. The more exact scientists’ warnings are, the better people can prepare for the storms.

Predictions are improving. “We’re gotten better over the years, especially the last few years,” says Phil Klotzbach, a scientist at an American university. How is a storm formed? Even if scientists know where a storm will happen, winds can suddenly change, carrying the storm to a new direction. “For a hurricane to happen, conditions have to be just right, ” Klotzbach says.

First, the ocean water needs to be warm enough so that it evaporates and rises into the air. As it rises, the vapor（水蒸气）cools and turns back into liquid. This process gives off heat. This produces energy like an engine that causes winds to increase. It drives the formation of a hurricane.

If wind speeds reach 40 miles per hour, the system is called a “tropical storm”, and it gets a name. At 75 miles per hour, it becomes a hurricane.

Hurricanes that hit the US start when a thunderstorm forms off the coast of Africa. Storms also develop over tropical waters in other parts of the world.

On average, 60 or 70 storms form off Africa every year. About 10 of them get names. There are usually about six hurricanes. Two tend to be very big, with winds of 115 miles per hour or higher.

The hurricane season lasts from June to November. Ninety percent of all hurricanes hit in August, September, and October. 

1. According to the passage, hurricanes usually ________.

A. form off the coast of Africa and America

B. travel at 40 miles per hour and get its name

C. cause sea winds to rise and blow over the sea

D. hit parts of the world in summer and autumn

2. The underlined word “evaporates” (in Paragraph 5) probably means “________”.

A. begins to move  B. gets lost    C. becomes hot       D. changes into gas

3. Which of the following about the information of a hurricane is the correct order?

a. The ocean water evaporates and goes into the air.

b. Heat creates energy and causes winds to increase.

c. The vapor cools.

d. The ocean water is warm enough.

e. The vapor changes back into liquid.

f. This course gives out heat.

A. a, d, e, b, c, f     B. a, b, c, f, d, e  C. d, a, c, e, f, b    D. d, a, b, c, e, f

4. According to the passage, the speed of the biggest two hurricanes reaches ______.

A.115 miles per hour                 B.110 miles per hour

C.75 miles per hour                  D.95 miles per hour

蒸汽的一般监督项目是（）。

A、钠、硅

B、导电、硬度

C、硬度、PH值

Inmarsat-F系统中，太平洋区的备用NCS是（）。

A、中国的北京（BEIJING）

B、新加坡的圣陶沙（SENTOSA.

C、日本的山口（YAMAGUCHI）

D、美国的圣保罗（SANTAPAULA.