Had he ever been on it? As sure as I am of anything, now. Yesterday and today, he was not on oxygen. Well, Im reassured! I am now at ease. I am sure that would have solved it.
Impossible worlds is a underscored phrase.
( z0 phrase :ARG1-of ( z1 underscore ) :domain ( z2 world :ARG1-of ( z3 possible :polarity - ) ) )
(z0 / phrase
    :ARG1-of (z1 / underscore-01)
    :domain (z2 / world
                :ARG1-of (z3 / possible-01
                             :polarity -)))
Impossible worlds is a underscored phrase .
z3 :polarity 0
z2 :ARG1-of z3
z0 :ARG1-of z1
z0 :domain z2