有这样一个命运多舛的民族，在德国法西斯统治时期，他们被剥夺了公民身份、几百万人惨遭屠杀。他们最有可能是(   )

有A、B、C、D四种物质。A是无色无味的气体．B在A中燃烧发出明亮的蓝紫色火焰，同时生成一种无色有刺激气味的气体C。D是一种无色的气体，纯净的D气体能在空气中安静的燃烧，发出淡蓝色火焰。试判断A、B、C、D各是什么物质，请将物质名称填在空格内。

A是____；B是____；C是____；D是____。

    Come and see the India elephants and the new tigers from America. The bears are waiting to meet you, and the monkeys from China are waiting to throw（扔） things to you. The lovely dogs from Australia are waiting to laugh at you. The giraffes from Brazil are waiting to look down on you.
Tickets                             Open time
Grown-up:（成人）$2.00             9:00a.m—4:00p.m
Children :over 12 $1.00               Except（除）Friday
Under12 Free(免票)                  10:00a.m—3:00p.m
Keep the zoo clean!
Don't touch(触摸) , give good food or go near the animals!