题目

根据短文内容，请将单词填写在题号对应的横线上。 Recently I have found many of us students spend too much time sending text messages or (play) games on cell phones, which has negative effects on our students and also does them to our eyes. Worse still, it is waste of time. We have little time to communicate our parents and friends. do we have time for physical exercise. What shall we do (improve) the situation? All of us should be (full) aware of the harmful effects of frequent use of cell phones. To begin with, let's limit our time (spend) on cell phones and start 下列有关种群和群落的叙述正确的是（ ）A.种群的存活曲线表示出生率和死亡率间的变化情况B.受灾的水稻呈斑状性的稀疏分布属于群落水平结构特征C.群落在环境条件相似的地段可以重复出现D.种群的外源性调节因素不会改变环境容纳量的大小