泡菜是用乳酸菌使蔬菜中的有机物生成乳酸.泡菜坛既要加盖,还要用一圈水来封口.其目的是( )
A:不让空气中的微生物进入菜坛内
B:防止尘土落入菜坛中
C:乳酸菌是厌氧菌,这有利于乳酸菌的发酵
D:杀死菜坛中的一些有害微生物
Food is very important to our health. Everyone needs to eat well if he or she wants to have a strong body.Our minds, like our bodies, always need the best food. This kind of food is knowledge. We start getting knowledge when we are very young.
图为澳大利亚和美国农业带及地形剖面图,读图回答下列问题:
若函数y=2﹣x+m的图象不经过第一象限,则m的取值范围是____
法律可以强制你赡养父母,但无法让你真正孝敬父母。”这句话说明( )