His ex-husband, whom she _________ last year, is now living in America.
----Why did you leave that position? ----I ______ a better position at IBM.
Some experts demanded that children _______ time to sleep and play.
The farmer used wood to build a house to store grain.
According to the periodic table, still some elements undiscovered.
Calculations, which are astronomically exact, have been made with the use of computers.