She is a quiet girl at school，but sometimes she _____ be very naughty.

--“Where is Tom?”--“He hasn’t come to school today, I think he ______be ill.”

If I _______ plan to do anything I wanted to, I’d like to go to Tibet and travel through as much of it as possible.

-Was the United State of America founded on July 4th, 1776？ --You _________  be right but I need to check it in the history textbook anyway.

(2013·安徽师大附中高三七模)Don't use water to put out the fire if oil catches fire. As is known, oil ________ float on water.