If amplitude of a wave is represented by $\mathrm{A} = \frac{\mathrm{c}}{\mathrm{a}+\mathrm{b}-\mathrm{c}}$ then the resonance will occur when: 

• A

  $\mathrm{b} = \frac{-\mathrm{c}}{2}$

• B

  $\mathrm{b} = 0 \mathrm{and} \mathrm{a} = \mathrm{c}$

• C

  $\mathrm{b} = -\frac{\mathrm{a}}{2}$

• D

  none