1 point -Which one of the following systems is causal? * O y(n)=x(n+2) y(t)=x(t)+x(t-3)+x(t^2) O y(t)=x(t-1)+x(t-2) O y(n)=x(2n^2) - Discrete-time signals are 1 point Continuous in amplitude and discrete in time Continuous in amplitude and continuous in time Discrete in amplitude and continuous in time Discrete in amplitude and discrete in time