A strain gauge is attached on a cantilever beam as shown. If the base of the cantilever vibrates according to the equation $x(t)=\sin\omega_1t+\sin\omega_2t,$ where $2\;\text{rad/s}<\omega_1,\;\omega_2<3\;\text{rad/s},$ then the output of the strain gauge is proportional to
- $x$
- $\frac{dx}{dt}$
- $\frac{d^2x}{dt^2}$
- $\frac{d(x-y)}{dt}$