Step 1: Resonance condition.
For resonance to occur, the length of the resonance tube must satisfy the condition where the tube supports standing waves. The formula for the frequency of resonance is:
\[
f = \frac{v}{2L}
\]
Where:
- \( f = 500 \, \text{Hz} \)
- \( v = 340 \, \text{m/s} \)
- \( L = 0.80 \, \text{m} \)
Step 2: Calculating the number of resonances.
The total number of resonances can be found by:
\[
N = \frac{v}{2fL}
\]
Substituting the known values:
\[
N = \frac{340}{2 \times 500 \times 0.80} = 4
\]
Thus, the correct answer is (B) 4.