稳定塔操作平稳要注意哪几方面？

放射性同位素工作终止工作前，需向卫生部门办理哪项手续（）。

A.许可手续

B.登记手续

C.变更许可手续

D.注销许可手续

E.豁免许可手续

骨样骨瘤的好发年龄为

A．21～30岁
B．11～20岁
C．20～40岁
D．30～60岁
E．2～4岁

（2011年四川广安，3题）下表是元素周期表中部分元素的原子结构示意图，请分析：

	ⅠA	ⅡA	ⅢA
第2周期
第3周期			X
第4周期	Y

⑴在化学反应中Mg原子易          （填“得”或“失”）电子；

⑵Na⁺离子核外的电子数为        ；

⑶经分析发现，元素的周期数与原子的电子层数、元素的主族数与原子的最外层电子数有着密切的关系；请推断X原子的最外层电子数为        ，Y原子的电子层数为        ；

⑷若镓(Ga)元素与氯元素只组成一种属于盐的化合物，请写出该化合物的化学式            。

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.