A：of
B：at
C：for
D：to
生物分类的依据是（ ）
In America, there are chores(杂活) for children of different ages. American people think that it's important to tell children their duty in the family.
Ages 4-6
Ages 6-12
Ages 13 and Up
-Make their bed;
-Clear dishes from the table;
-Set the table;
-Get the mail from the mailbox;
-Take care of pets;
-Cook simple food;
-Help wash the car;
-Vacuum(吸尘) and sweep;
-Take out the rubbish.
-Wash windows;
-Clean out fridge;
-Prepare a meal;
-Make shopping lists;
-Mow the lawn(剪草坪)
﹣5的绝对值是
以下关于二战说法正确的是（ ）
某兴趣小组参观学校食堂，发现其中蕴含丰富的化学知识．
（1）下列食堂中的常见用品，其主要材料属于合成材料的是 ____（填字母）．
A、棉布围裙 B、陶瓷碗 C、不锈钢锅 D、塑料桶
（2）同学们在食堂外就闻到了菜香，用粒子观点解释其原因： ____．
（3）食堂使用的是加碘盐，这里的“碘”指的是 ____（填“单质”、“元素”或“原子”），食用加碘盐有利于补充 ____（填营养素的名称）．
（4）做好饭菜，关闭燃气阀门，使火焰熄灭的原理是 ____．
