问题
选择题
Oxygen usually ______ in the form of gas in nature but when made cold enough, it can also take
the form of solid. [ ]
A. remains
B. stays
B. exists
D. survives
答案
答案:B
Oxygen usually ______ in the form of gas in nature but when made cold enough, it can also take
the form of solid. [ ]
A. remains
B. stays
B. exists
D. survives
答案:B