People in flooded areas suffered a lot,without drinking water,electricity and ________food supply,so they continued to flee the town.
A:suitable
B:content
C:handy
D:adequate
如图,⊙O的半径均为R.
某人估测一竖直枯井深度,从井口静止释放一石头并开始计时,经2s听到石头落地声,由此可知井深约为(不计声音传播时间,重力加速度g取10m/s2)( )
A
B
C
D
强电解质
Cu
NaCl
HNO3
BaCO3
弱电解质
CH3COOH
NH3
Fe(OH)3
H3PO4
非电解质
酒精
BaSO4
H2O
蔗糖
硼酸能够吸收中子,屏蔽核辐射.硼酸晶体具有层状结构,其每一层结构如图所示