John did not feel well yesterday; otherwise, he ________to see his friend off at the airport.
句意： 约翰昨天感到不舒服， 否则， 他就会去机场给朋友送行了。 本题考查虚拟语气。 Otherwise 相当于 if he had felt well， 是隐含的虚拟语气， 因此从句用 would have done 表示和过去相反的事情。