在太空舱里，为了保持舱内CO2气体含量相对稳定，常用NiFe2O4作催化剂将宇航员呼出的CO2转化为O2，NiFe2O4中铁为+3价，则Ni的化合价为
| A．+1 | B．+2 | C．+3 | D．+4 |
相关试题
more, and you'll improve your spoken English.
| A． | Speak | B． | Speaks | C． | Speaking | D． | To speak |
--- I've just got a postcard from my pen friend.
--- Let me have a look
. Wow.nice card!
| A． | What | B． | What a | C． | How | D． | Why |
--- What is your favourite sport?
--- Swimming, I think. It's of all.
| A． | earsier | B． | more difficult | C． | the most interesting | D． | the most boring |
---I use your ruler, Lingling?
--- Sure. Here you are.
| A． | May | B． | Would | C． | Need | D． | Must |
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