Scientists are still wondering ________ the Egyptians built the pyramids so long ago.
The students are talking about the strange people and stories ____ they met in the adventure.
It is not I but Mr.Green who____in charge of the company.
After living with his grandparents in the countryside fort en years, the boy returned to The big city____his parents worked.
He was impolite to theCustom Officer,____,of course,made things even worse.
Soon they got to the bank,____stood a big pine tree.