In order to ________ consumers, it's extremely important to consider what information should be included in the advertisement.
--- Who ______ it be that is singing in the next room? --- It _______ be Lucy, but I am not sure.
Not until World War II ______ to use new chemical techniques to purify penicillin.
--- What did the manager say at yesterday’s meeting? --- So you______ to him carefully.
--- Did Jack come back early last night? --- Yes. It was not yet eight o’clock ______ he arrived home.
In some countries citizens are ______ to vote, and if they don’t they get fined.