Answer:
A. Water
Explanation:
H2O means that there are two hydrogen and one oxygen in every water molecule.
The volume did not change, it remained at 20 ml
<h3>Further explanation</h3>
Given
20 ml a sample gas at STP(273 K, 1 atm)
T₂=546 K
P₂=2 atm
Required
The volume
Solution
Combined gas Law :

Input the value :

The volume does not change because the pressure and temperature are increased by the same ratio as the initial conditions (to 2x)
The variables in the ideal gas constant has V as the unit of liters and T has the unit of Kelvin. Thus, option C is correct.
The gas constant in an ideal gas equation has been the value of the energy absorbed by 1 mole of an ideal gas at standard temperature and pressure.
The value of R has been dependent on the units of volume, temperature and pressure of the ideal gas.
The given value of R has been 0.0821 L.atm/mol.K
The unit in gas constant has been L (Liter) for volume (V).
The unit of pressure (P) has been atm.
The unit of temperature (T) has been Kelvin (K).
Thus the gas law constant used by student has V has the unit of liters and T has the unit of Kelvin. Thus, option C is correct.
For more information about the gas constant, refer to the link:
brainly.com/question/24814070