任何国家的主食很大程度上来自于在该国气候和土壤条件下长的最好的农作物。
经过无数次的尝试后，成功的几率和失败的几率是相等的。
大多数物体一旦冻结后就会缩小，因此固体的密度要比液体的密度高的多。
The chief food eaten in any Country depend largely on what grows best in its climinate and soil.
Over a large number of trials,the probability of the event\'s occuring is equal to the probability that it will not occur.
Most sunstance contract when they freeze so that density of a substance\'s solid is higher than the density of its liquid.
