Answer:-
A. A water molecule
Explanation:-
A molecule is the smallest particle of a compound that retains all it's chemical properties.
Here H2O is a compound. So the smallest particle that will retain all the chemical properties and still remain water is water molecule.
Atoms Hydrogen and Oxygen both have different chemical properties from water H2O and are thus different.
Hydrogen peroxide is different molecule from water. So it is also not water.
C. 2Fe2O3 would be the correct answer!
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
Answer:

Explanation:
1. Calculate the decay constant
The integrated rate law for radioactive decay is 1

where
A₀ and A_t are the counts at t = 0 and t
k is the radioactive decay constant

2. Calculate the half-life

The half-life for decay is
.