Tom ________ with his aunt and uncle because his parents have gone abroad for a holiday.
A：is staying
B：stays
C：stayed
D：had stayed
食物链中生产者与消费者之间的关系是（ ）
下列各组化合物中，铁元素的质量分数按由低到高的顺序排列的是
①加强国有企业高管薪酬管理
②建立科技成果入股、岗位分红权激励办法
③提高城乡居民最低生活保障标准
④加大保障性住房供给
