―Do you know where David is? I couldn’t find him anywhere.―Well. He ______ have gone far — his coat’s still here.

---- May I smoke here?--- If you      , choose a seat in the smoking section.

A giant of a man was standing in the doorway. His face was almost completely hidden by a long and untidy hair and a wild beard, but you ______ make out his eyes, shining like black beetles under all the hair.

--- _________ David be the new chairperson of the Students’ Union? --- He ________ be, but I’m not sure.

(2013·江西六所重点高中一模)We ________ take clean drinking water for granted. One day we may run out of it.