Bob's heartbreak<br>Bob is happily married. He brings home some flowers for his wife. While looking for his wife he sees her with another man. Bob throws the flowers down and leaves. Bob is heartbroken by his wife cheating.
Bob had an expectation of a monogamous marriage.
Bob is clearly upset when he finds his wife with another man, and if there were no expectation of monogamy, that would not be the case. 
( z1 expect :ARG0 ( z2 person :name ( z3 name :op "Bob" ) ) :ARG1 ( z4 marry :mod ( z5 monogamy ) ) )