Question $4(6$ points$)$

Consider the differential equation

$y^{\text{'}\text{'}}+9y=cos(t)$

Select all true statements.

None of the other options displayed.

Resonance is not possible in this case, since there is no friction.

When $=9\mathrm{.}01,$ the solution will exhibit beats.

When $=3\mathrm{.}01,$ the solution will exhibit beats.

When $=3,$ the solution will exhibit resonance.

Resonance happens when the driving frequency equals the natural frequency, in the absence of friction.

When $=9,$ the solution will exhibit resonance.

When $=2\mathrm{.}99,$ the solution will exhibit beats.

Beats happens when the driving frequency equals the natural frequency, in the absence of friction.

When $=3,$ the solution will exhibit beats.