Consider a real baseband signal $x(t)=e^{-2 t}$, for $t$ (in seconds) $\geq 0$. If $99 \%$ of energy of $x(t)$ lies within $B \mathrm{~Hz}$, then which of the following options is TRUE for the value of $B$ ?

Consider the discrete time system $(S)$ with input $x[n]$ and output $y[n]$ as shown in the Figure. The two sub-systems represented by their impulse responses $h_1[n]$ and $h_2[n]$ are linear and time invariant.

Which of the following statements is necessarily TRUE?

Let $x_1(t)=\cos (2 \pi n t)$ and $x_2(t)=2 \sin (4 \pi n t)$ represent two sinusoids for a positive integer $n$ and $-\infty

Which of the following statements about $x_1(t)$ and $x_2(t)$ is/are valid?

Among the following options, the antonym of the word 'nocturnal' is $\_\_\_\_$ .