求证：△BDE是等腰三角形．

邓小平理论第一次比较系统地回答了什么是社会主义、怎样建设社会主义等一系列基本问题，是马克思主义在中国发展的新阶段。

    Everyone has a family name. In China, the family name is the first name, but in English countries(国家)the family name is the last name. Do you know how English people get their family names? And what do they mean(意味着)? English people usually get their family name in these ways (方式).

    Some family names come from the places(地方)of their homes. A man live(住)on or near a hill, his family name may be (可能是) Hill. In England(英国), people's names may be Wood, Lake because they live near the wood or the lake.

    Some family names come from a person's job(职业). If a man is a cook, his family name may be Cook.

    And many people get their family names from their father's family names. If you hear(听到) the name "Jackson", you can know that he is the son of Jack.

核电站是利用铀核在____ （选填“裂变”或“聚变”）时释放的能量来发电，在核反应堆中，发生的链式反应是____ （选填“可控”或“不可控”）的．