A:体积大小:④>③>②>①
B:原子数目:③>①>④>②
C:密度大小:④>②>③>①
D:质量大小:④>③>②>①
写出复数句。
Model: This is an old box.
These are old boxes.
This is a ruler.
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某二肽(分子式:C7H12O5N2),由1分子谷氨酸和1分子甘氨酸脱水缩合而成,已知谷氨酸为C5H9O4N,则甘氨酸的分子式为( )