搜题请搜索小程序“爱下问搜题”
问题 选择题

下列物质中，属于氧化物的是（　　）

A．KMnO4

B．KOH

C．ClO2

D．H2SO4

答案

A、KMnO4含有三种元素，不是氧化物，故A错误；

B、KOH含有三种元素，不是氧化物，故B错误；

C、ClO2含有两种元素且含有氧元素，属于氧化物，故C正确；

D、H2SO4含有三种元素，不是氧化物，故D错误；

故选C．

单项选择题

In the second half of each year, many powerful storms are born in the tropical Atlantic and Caribbean seas. Of (91) , only about half a dozen (92) the p, circling winds of 75 miles per hour or more that give them hurricane status, and several usually (93) their way to the coast. There cause millions of dollars of (94) , and bring death to (95) numbers of people.
The great storms that hit the coast start (96) innocent circling disturbances hundreds, even thousands of miles out to sea. As they travel aimlessly over water (97) by the summer sun, they are carried westward by the (98) winds. When conditions are just (99) , warm, moist air flows in (100) the bottom of such a disturbance, moves upward through it and comes out at the top. In the (101) , the moisture in this warm air produces rain, and with it the heat is converted to energy in the form of p winds. As the heat increases, the (102) hurricane begins to swirl in a counter-clockwise motion.
The average life of a hurricane is only about nine days, but it contains almost (103) power than we can imagine. The energy in the heat released by a hurricane’s rainfall in a(n) (104) day would (105) the entire electrical needs of the United States for more than six months. Water, not wind, is the main (106) of death and destruction in a hurricane. A(n) (107) hurricane brings 6-to 12-inch downpours (108) in sudden floods. (109) is the powerful movement of the sea-the mountains of water moving toward the low-pressure hurricane center. The water level (110) as much as 15 feet above normal as it moves toward shore.

A．as

B．with

C．from

D．at
查看答案
单项选择题

电动机结构防护型式第一位表征数字2表示的防护等级含义为（）。

A.垂直滴水应无有害影响

B.当电机从正常位置向任何方向倾斜至15。以内任一角度时垂直滴水应无有害影响

C.与铅垂线成60°范围内的淋水应无有害影响

D.承受任何方向的溅水应无有害影响
查看答案