H2O is the correct answer :)
Answer:
C
Explanation:
Characteristics used to classify stars include color, temperature, size, composition, and brightness.
N=N₀*2^(-t/T)
N₀=200 g
T=10 d
t=30 d
N=200*2^(-30/10)=25 g
25 g will remain
Fixed density
Particles move smoothly