Identify the correct statements :
A. The molality of $2.5$ g of ethanoic acid (Molar mass : $60$ g mol$^{-1}$) in $75$ g of benzene solution is $0.556$ m.
B. The molarity of a solution containing $5$ g of NaOH (molar mass : $40$ g mol$^{-1}$) in $450$ mL of solution is $0.278$ M at $298$ K.
C. Aquatic species are more comfortable in cold water.
D. The solubility of gas increases with decrease in pressure.
E. For a binary mixture of A and B, the number of moles of A and B are $n_A$ and $n_B$ respectively. The mole fraction of B will be $x_B = \dfrac{n_A}{n_A + n_B}$.
Choose the correct answer from the options given below :

Statement A : Molality is given by the number of moles of solute divided by the mass of solvent in kg.
Moles of ethanoic acid $= \dfrac{2.5}{60} = \dfrac{1}{24}$ mol
Mass of benzene $= 75$ g $= 0.075$ kg
Molality $= \dfrac{1/24}{0.075} = \dfrac{1000}{24 \times 75} = \dfrac{1000}{1800} = \dfrac{5}{9} = 0.556$ m
Statement A is correct.

Statement B : Molarity is given by the number of moles of solute divided by the volume of solution in litres.
Moles of NaOH $= \dfrac{5}{40} = \dfrac{1}{8}$ mol
Volume of solution $= 450$ mL $= 0.45$ L
Molarity $= \dfrac{1/8}{0.45} = \dfrac{1000}{8 \times 450} = \dfrac{1000}{3600} = \dfrac{5}{18} = 0.278$ M
Statement B is correct.

Statement C : The solubility of gases (like oxygen) in water increases with a decrease in temperature. Therefore, cold water contains more dissolved oxygen, making aquatic species more comfortable.
Statement C is correct.

Statement D : According to Henry's law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas. Thus, solubility decreases with a decrease in pressure.
Statement D is incorrect.

Statement E : The mole fraction of component B is the ratio of the number of moles of B to the total number of moles in the mixture.
$x_B = \dfrac{n_B}{n_A + n_B}$
Statement E is incorrect.

Therefore, only statements A, B, and C are correct.

Answer: A, B and C only