Answer: a. It receives a hydrogen ion.
Explanation: Base is a species which is capable of donating its negative quantity and accepting the positive one.
For example, ammonia is considered as a base because it is capable of donating its lone pairs of electrons and can accept an proton as well.
Here, out of the given options, Hydrogen 
is a proton which is acting as a positive species and hydroxide ion 
is a negative species.
Thus, option (A) is the correct answer as it will receive a hydrogen ion from another base making itself a conjugate acid.
The answer is A, mass and volume.
The equation for density, <span>ρ,</span> is ρ = m/V. m is mass and V is volume.
The volume of the gas at a temperature of 405.0 K would be 607.5 mL. Making option D the right answer to the question.
What is the volume of the gas?
To find the volume of the gas, the equation to be used would have to be combine gas law.
Combine gas law as the name suggest uses the combination of Charles law which measures Volume against temperature, and Gay-Lussac's law which measures Pressure/Temperature, and Boyle's law which measures pressure X volume where k is constant.
Using the combine law to find the volume, we have:
P₁V₁/T₁=P₂V₂/T₂
Where P₁ = initial pressure
V₁ = initial volume
T₁ = initial temperature
P₂ = final pressure
V₂ = final volume
T₂ = final temperature
P₁ = 2.25atm
V₁ = 450.0 mL
T₁ = 300 K
T₂ = 405.0 K
V₂ = ?
D) 607.5 mL
= [2.25(450)]÷300=[2.25(V₂]÷405
Making V₂ the subject
3.375=2.25 V₂ ÷ 405
V₂ = 3.375 x 405 ÷ 2.25
V₂ = 607.5 mL
In summary, a gas with an initial pressure of 2.25atm, an initial pressure of 450.0 mL and an initial temperature of 300 K would have a final volume of 607.5 mL if the temperature is increased to 405.0 K.
Learn more about Combine gas law here: brainly.com/question/13538773
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