Bad Qubits — Learn Quantum by Doing

Multiple choice

Recall the CHSH quantity S = E(0,0) + E(0,1) + E(1,0) - E(1,1) with binary +-1 outcomes. What value does S take for any local hidden-variable theory versus the maximum reachable by quantum mechanics on a maximally entangled (singlet) pair?

Local hidden-variable theories obey |S| <= 2; quantum mechanics reaches S = 2*sqrt(2) ~ 2.828
Local hidden-variable theories and quantum mechanics both obey |S| <= 2; only super-quantum boxes exceed it
Local hidden-variable theories obey |S| <= 2*sqrt(2); quantum mechanics reaches S = 4
Local hidden-variable theories obey |S| <= 1; quantum mechanics reaches S = 2