question: What is the difference between signal-aware and signal-agnostic samplers? option 1: Signal-aware samplers consider the instantaneous estimation error, while signal-agnostic samplers consider the expected estimation error option 2: Signal-aware samplers use causal knowledge of the signal, while signal-agnostic samplers do not option 3: Signal-aware samplers minimize the time-average age penalty, while signal-agnostic samplers minimize the mean-squared reconstruction error option 4: Signal-aware samplers are optimal for discrete-time systems, while signal-agnostic samplers are optimal for continuous-time systems 