a is the answer
Explaination: By Avogadro's Law, if the temperature and pressure of two ideal gases is the same, the number of gas particles in each gas would be proportional to the volume of that gas.
All four gas samples in this question share the same temperature and pressure. Hence, if all these gases are ideal gases, the number of gas particles in each sample would be proportional to the volume of that sample. Two of these samples would contain the same number of gas particles if and only if the volume of the two samples is equal to one another.
The second choice,
200
m
L
200mL of neon
N
e
(
g
)
Ne(g) at
2
5
∘
C
25
∘
C and
1
a
t
m
1atm , is the only choice where the volume of the sample is also
200
m
L
200mL . Hence, that choice would be the only one with as many gas particles as
200
m
L
200mL of
H
e
(
g
)
He(g) at
2
5
∘
C
25
∘
C and
1
a
t
m
1atm .