填空题
In nineteenth-century America, most migrants went west because the region seemed to promise a better life.
Life on the farm, however, was much harder than it was (36) Migrants often encountered shortages of (37) they had once taken for granted. The open grassland contained little wood for (38) and fuel. Water was sometimes (39) as well. Few families were lucky or wealthy enough to buy land near a stream that did not dry up in summer and (40) in winter.
The weather was seldom predictable. In summer, weeks of extreme heat and dry winds often gave way to violent storms that washed away crops and (41) . In winter, the wind and cold from blizzards piled up (42) snowdrifts that halted all outdoor movement. The storm trapped schoolchildren and killed several parents who (43) out to rescue them. (44) . In the fall, a week without rain could turn dry grasslands into tinder, and the slightest spark could ignite a raging prairie fire.
Nature could be cruel even under good conditions. (45) . Worms and flying pests ravaged corn and wheat. Heralded only by the din of buzzing wings, a mile-long cloud of insects would smother the land and eat up everything: plants, tree bark, and clothes. (46) .