横向
1
Compound containing oxygen
5
Substance with pH below 7
7
Group of similar cells
8
Unit of heredity
9
Second lightest element
10
Infectious microscopic agent
12
Biological catalyst
纵向
2
Mass per unit volume
3
Natural satellite of Earth
4
Disturbance that transfers energy
6
Naturally occurring inorganic solid
11
Push or pull on an object