d
Let molar mass of protein \(A=x\) \(g/mol\) 

Let molar mass of protein \(B = y g / mol\)

\(\pi_{ A }=\) osmotic pressure of protein \(A =\frac{\left(\frac{0.73}{ x }\right)}{0.25} RT\)

\(\pi_{ B }=\) osmotic pressure of protein \(B =\frac{\left(\frac{1.65}{ y }\right)}{1} RT\)

\(\pi_{ A }=\pi_{ B }\)

\(\Rightarrow\left(\frac{0.73}{ x \times 0.25}\right) RT =\left(\frac{1.65}{ y }\right) RT\)

\(\Rightarrow\left(\frac{ x }{ y }\right)=\frac{0.73}{0.25 \times 1.65}=1.769 \cong 1.77\)