Show that the truth table given in Table 7.3 can

Show that the truth table given in Table 7.3 can be constructed by combining the following two steps:
(a) The message signal b(t) and PN signal c(t) are added modulo-2.
(b) Symbols 0 and 1 at the modulo-2 adder output are represented by phase shifts of 0 and 180 degrees, respectively.