下列物质的用途与该物质的物理性质有关的是（ ）
A．用硫酸除去金属表面的铁锈
B．用氧气炼钢、炼铁
C．用氢气作高能燃料
D．用干冰进行人工降雨
答案：D
题目分析：物理性质：物质不需要化学变化就表现出的性质。包括：颜色、状态、气味、熔点、沸点、密度、硬度、溶解性、挥发性、延展性、导电性、吸水性、吸附性等，化学性质：物质在化学变化中表现出来的性质。可燃性、氧化性、还原性、活泼性、稳定性、腐蚀性、毒性、金属活动性等，A、用硫酸除去金属表面的铁锈，是利用酸的化学性质，能与金属氧化物反应，属于化学性质，B、用氧气炼钢、炼铁，是利用氧气的助燃性，属于化学性质，C、用氢气作高能燃料，是利用氢气的可燃性，属于化学性质，D、用干冰进行人工降雨是利用干冰升华吸热，是周围的温度降低，属于物理性质，故选D
Passage Two
| With unemployment rising and housing costs still high, cities around the country are experiencing a new and sudden wave of homelessness. Shelters are overflowing, and more people this year are sleeping on floors in dingy social service centers, living in cars or spending nights on the streets. In New York, Boston and other dries, homelessness is at record levels, a consequence of a faltering (摇晃的) economy that has crumbled even further after the Sept. 11 attacks. A survey by the U. S. Conference of Mayors released last week found that requests for emergency shelter in 27 cities had increased an average of 13 percent over last year. The report said the increases were 26 percent in Trenton; 25 percent in Kansas City, Mo.; 22 percent in Chicago; 20 percent in Denver; and 20 percent in New Orleans. An unusual confluence of factors seems to be responsible for the surge. Housing prices, which soared in the expansion of the 1990’s, have not gone down, even though the economy has tumbled. A stream of layoffs has newly unemployed people taking low-wage jobs that might have otherwise gone to the poor. Benefits for welfare recipients are expiring under government imposed deadlines. And charitable donations to programs that help the disadvantaged are down considerably, officials around the country said, because of the economy and the outpouring of donations for people affected by Sept. 11. "This is an unprecedented convergence (集中) of calamities (灾难) ," said Xavier De Souza Briggs, an assistant professor of public policy at the John F. Kennedy School of Government at Harvard. "It’s really a crisis. " More than half the cities surveyed by the mayors’ group reported that in the last year people had remained homeless longer, an average of six months. There is no total number for the homeless nationwide. Experts said it was difficult to compare the situation with statistics in previous decades, because counting methods have improved. Yet, several experts said they believed that the increases reported by cities like Boston and Chicago reflected a national trend. "My impression is there is more homelessness now than there was 20 years ago," Gary Burtless, an economist at the Brookings Institution, said, adding that he believed that economic factors were not the sole explanation. "I think that there must be a greater segment of our population that has tenuous connections to family and friends, and therefore has fewer resources to fall back on when something very bad happens like when they lose their job," he said. |
Which of the following is NOT a reason for the increase of homelessness
A．Unemployment.
B．Housing prices.
C．Sept. 11 attacks.
D．Floods.