If you spend the spring sneezing, take a look at your plate. Some foods _____ make allergies worse.

—When I first got to Harvard, my awkward English brought me great trouble.——Oh, dear, it _______a struggle for you to keep up with other students.

—Is Jack on duty today? —It ______ be him. It is his turn tomorrow.

—Must I go through the radiation (辐射) check when I come back from Japan at the airport these days?—Yes, you ______. 

—Look at the man in the classroom! Is he Mr. White?—No, it __________be him. He’s eating in the dining hall.