--- Another cup of coffee? ---No. thanks. I _____ be off. Marry is waiting for me.

--Is Professer Smith giving the speech today?--It ________ be him. He is abroad right now.

--It is really fun to hike and I often go hiking in the forest.--But hiking alone in the forest ______ be very dangerous.

You________ drink it, for it is poisonous.

I can’t go to the cinema with you because I  _______ stay here until my mother comes back.