Step 1: Find the radius ratio
A has four times the pressure, so a radius four times smaller.
Step 2: Cube it
Volume ratio $=\left(\tfrac14\right)^3=\tfrac1{64}$, and same density gives the same mass ratio, so $1:64$, option (D).
Final Answer:
The ratio is $1:64$, option (D).
\[ \boxed{1:64} \]