Is this the problem ____the teacher explained last week ? Choose the wrong answer :

The new tax would force companies to__________energy-saving measures.

He knows so much about Russia that he’s universallyacknowledged as a _____ on Russian affairs.

Nobody believed his reason for being absent from theclass he had to meet his uncleat the air port

Their university is located on a beautiful lake, _____ of this developing city [ ]