1994年,苏梅尔一列维彗星裂成二十多块碎片撞向木星,产生巨大的爆炸,但是身处地球的人们却没有听到一丝声响,这是什么原因 ( )
Beethoven is a very____ (著名的)musician .I'm____ (紧张的)out because I can't find the way home.My mother often____ (担心)about my father's health..She likes to s____ e-mails at school.Lily is very t____ , she'd like to have some water.
我国的直辖市有( )①北京 ②上海 ③哈尔滨 ④天津 ⑤深圳 ⑥重庆
下列正多边形中,中心角等于内角的是( )