下面是用托盘天平称石块质量的实验步骤，请填上适当内容．

A．把天平放在 ____桌面上．

B．将游砝拨到标尺左侧 ____上．

C．调节横梁上的 ____（游码或平衡螺母），使横梁平衡．

D．将被测物体放在天平的 ____盘，右盘放 ____，并调节 ____（游码或平衡螺母）位置，使指针指在分度盘中线处．

E．计算砝码的总质量加上游码所对刻度值得出物体的质量．

My father's day

    My father is a teacher. He teaches Chinese. He likes his job and his students. And the students like him too. He goes to work from Monday to Friday. He does not work on Saturday and Sunday. Every day, he gets up at five thirty. At six, he has breakfast. Then he goes running. He goes to school at seven. He has lunch at school. He goes home at five in the afternoon. At six o'clock, he has dinner. He doesn't watch TV. He likes reading（读）books with me. He goes to bed at nine thirty.

A．铝元素位于元素周期表中的第四周期

B．铝的相对原子质量为26.98g

C．铝原子在化学反应中容易失去电子

D．氧化铝的化学式为____．