_____nocauseforalarm,theoldmanwentbacktohisroom.

Theopeningceremonyisagreatoccasion.Itisessential_____forthat.

It was recommended that passengers _____ smoke during the flight.

_____enoughtimeandmoney,theresearcherswouldhavebeenabletodiscovermoreinthisfield.

Professor Johnson is said _____ some significant advance in his research in the past years.