已知甲、乙、丙、丁四种无机物均由原子序数为前18号的元素组成,且它们之间的转化关系如下:,下列说法正确的是( )
A:甲一定为单质
B:丙一定为氧化物
C:丁一定为酸
D:甲、乙、丙、丁的相对分子质量一定是16或16的倍数
(2015.福建莆田)
Enjoy Harvesting
Want to relax yourself?
Want to experience country life?
Come and pick litchi!
Free for a taste.
Price:¥20 per kilo Dates: July 20th-July 28th
Add: Changlin village Tel:277-8688
Fitness Band on sale
Smartwatches without the watch
Monitor speed, time, distance, caloties burned, etc.
Long battery(电池)life (5 days)
¥800 (20% off for students)
Tel:289-6799
Visit Sam Mall for more information.
Ice and Snow Festival
Charming Ice Carving
Amazing World of Ice and Snow
Welcome to Fenghuang Park!
Dates: July 1st -July 25th
¥20 for each adult (half for each student)
Tel:288-6299
Super Pillow(枕头)Fight Party
Pillow Fight, a popular activity among young foreigners, has now come to Putian. It's a creative way to release(释放) pressure and stress.
Place:Putian Stadium
Time:2:30-5:00pm, June 28th
Fee:¥50 (pillow included)
Tel:275-6588
计算(﹣2ab2)3÷(﹣4ab)2的结果是____ .
“普天之下,莫非王土;率土之滨,莫非王臣。”这句话反映了西周的( )
如图所示,A、B为两块足够大的相距为d的平行金属板,接在电压为U的电源上.在A板的中央P点放置一个电子发射源.可以向各个方向释放电子.设电子的质量为m、电荷量为e,射出的初速度为v.求电子打在B板上的区域面积?(不计电子的重力)
计算:
(1)(48﹣418)﹣(313﹣20.5)
(2)8+482-12-2-32.