Step 1: Understanding the Concept
The speed of sound in an ideal gas is \(v=\sqrt{\dfrac{\gamma RT}{M}}\). Both gases are monatomic, so \(\gamma=\dfrac53\) for each. The temperature is the same.
Step 2: Ratio
\[ \frac{v_1}{v_2}=\sqrt{\frac{M_2}{M_1}}=\sqrt{\frac{m_2}{m_1}} \]
Step 3: Meaning
A heavier gas has a smaller speed of sound. Gas 1 with larger molecular mass \(m_1\) is slower, so the ratio has \(m_2\) on top.
Step 4: Check the options
Option (A) is the inverse. Options (C) and (D) lack the square root. So the answer is (B).
Final Answer:
At equal temperature the speed varies as one over root of molecular mass, so the ratio is root of m2 over m1, option (B).
\[ \boxed{\sqrt{\frac{m_2}{m_1}}} \]