读下图，回答下列问题。
小题1:该图是“我国某两种农作物优势产区分布示意图”，图中①②代表的农作物是
A．①大豆②棉花
B．①甘蔗②油菜
C．①油菜②大豆
D．①棉花②甘蔗小题2:导致我国南北方地区耕作制度存在明显差异的主导因素是
A．土壤
B．水分
C．热量
D．地形
小题1:D
小题2:C
题目分析：
小题1:我国的①棉花主要分布于长江、黄河的中下游地区，新疆是我国最大的长绒棉生产基地，糖料作物中，②甘蔗性喜湿热，主要分布在华南地区，广西为最大产区，广东、云南亦生产较多，甜菜性喜温凉，主要分布在新疆、黑龙江、内蒙古等地。
小题2:我国南方和北方耕作制度、农作物有明显差异，北方平原广阔，耕地多，但热量较低，降水较少，以旱地为主，主要农作物是小麦；南方多丘陵、山地，但热量高，降水丰沛，以水田为主，主要农作物是水稻，其中，导致我国南北方耕作制度和农作物差异的主导因素为热量的显著差异。
Passage Three
| Immigrants are consumers as well as producers, so they create jobs as well as taking them. And the work they do need not be at the expense of native workers. Immigrants often hold jobs that natives are unwilling to accept at any feasible wage. Also, immigrants sometimes help to keep industries viable (能存活的) that would otherwise disappear altogether, causing employment to fall. This was the conclusion of a study of the Los Angeles garment industry in the 1970s and 1980s. And when immigrants working for low wages do put downward pressure on natives’ wages, they may raise the (real) wages of natives in general by keeping prices lower than they otherwise would be. In theory, then, the net effect of immigration on native wages is uncertain. Unfortunately, most of the empirical (经验主义的) research on whether immigrants make natives worse off in practice is also inconclusive except the effect, one way or the other, seems small. Most of this research has been done in America: if there were any marked influence on wages, that is where you would expect to find it, given the scale of immigration and the tendency of the newcomers to concentrate in certain areas. But most studies have compared wages and employment in areas with many immigrants to wages and employment in areas with few. For instance, one examined the impact of sudden and notorious inflow of refugees to Miami from the Cuban port of Mariel in 1980. Within the space of a few months, 125 000 people had arrived, increasing Miami’s labor force by 7%. Yet the study concluded that wages and employment among the city’s natives, including the unskilled, were virtually unaffected. Another study examined the effect of immigration on wages and employment of those at the bottom of the jobs ladder—unskilled blacks and Hispanics. It found that a doubling of the rate of immigration had no detectable effect on natives. The most recent work, admittedly, has tended to question these findings. Using more detailed statistics and more sophisticated methods than the earlier studies, this work has tended to find that immigrants’ wages take longer to rise to the level of the natives’ wages than has been supposed. This implies a more persistent downward pressure on the host economy’s labor market. Typically these studies find that immigration does depress unskilled natives’ wages to a small extent. But nearly all economists would agree that the effects of immigration are insignificant in relation to other influences. |
According to the Los Angeles study, immigrants ______.
A．sometimes help to maintain the existence of some industries
B．sometimes cause employment to fall
C．may lower the wages of natives in general
D．may help promote inflation