In recent years much more emphasis has been put______ developing the students productive skills.

Thisrobotissupposedtosavealotoflabor,butitremainsaproblemifit______.

InfactPeterwouldratherhaveleftforSanFranciscothan____inNewYork.

You______bedrivenoutoftheschoolifyoudaretocheatintheexam.

Tina _____ have known the truth, or she would have told us.