premise: The man and woman are both smiling.
hypothesis: A man and a woman smile as the watch the children play.
explanation_1: They don't need to watch the children play to smile. It's likely they're making each other smile, rather than the children.
explanation_2: There is nothing prior  mentioned about the man and woman having a smile as the watch the children play.
explanation_3: Just because they are smiling doesn't imply that they are watching children.
premise_logic: exists e1 s1 x1 x2 x3.(n_woman(x3) & n_man(x2) & subset_of(x3,x1) & subset_of(x2,x1) & a_both(s1) & Manner(e1,s1) & Actor(e1,x1) & v_smile(e1))
hypothesis_logic: exists s1 x1 x2 x3 x4 x5 x6.(n_watch(x4) & a_topic(s1) & subset_of(x2,s1) & as(x2,x4) & n_play(x5) & of(x5,x6) & n_child(x6) & (x4 = x5) & n_smile(x2) & of(x2,x3) & n_woman(x3) & subset_of(x1,s1) & n_man(x1))
premise_sim: exists e1 s1 x1 x2 x3.(v_smile(e1) & subset_of(x3,x1) & subset_of(x2,x1) & n_woman(x3) & n_man(x2) & a_both(s1) & Manner(e1,s1) & Actor(e1,x1))
hypothesis_sim: exists s1 x1 x2 x3 x4 x5 x6.(subset_of(x2,s1) & subset_of(x1,s1) & of(x5,x6) & of(x2,x3) & n_woman(x3) & n_watch(x4) & n_smile(x2) & n_play(x5) & n_man(x1) & n_child(x6) & as(x2,x4) & a_topic(s1) & (x4 = x5))