With the following equations, the time invariant systems are
$$\eqalign{ & 1.\,\frac{{{d^2}y\left( t \right)}}{{d{t^2}}} + 2t\frac{d}{{dt}}y\left( t \right) + 5y\left( t \right) = x\left( t \right) \cr & 2.\,y\left( t \right) = {e^{ - 2x\left( t \right)}} \cr & 3.\,y\left( t \right) = \left[ {\frac{d}{{dt}}x\left( t \right)} \right] \cr & 4.\,y\left( t \right) = \frac{d}{{dt}}\left[ {{e^{ - 2t}}x\left( t \right)} \right] \cr} $$

A. 1 and 2

B. 1 and 4

C. 2 and 3

D. 3 and 4

Answer: Option C