What does the sign mean

______ bargaining is always such great fun—Usually people consider it a test to see who can stand their ground longer.

Theresearchonthenewbirdfluvirusvaccmeischallenginganddemanding.Whodoyouthink candothejob?— _____ mystudentshaveatry?[ ]

Before I talked with ______ scientist, Ihad never met______ clever person like him.

It was announced that only when the fire was _________ would residnts(居民) be permitted to return to their homes