Yesterday morning I was just leaving_______ the telephone rang.
–Who’s that boy?–Liang Bo. He is _____ very popular singer in Voice of China.
---Where do Tom and John sit ?--- Tom sits __________ of the room and John sits _________ of the room.
---Is Lucy ______ her homework?--- No , she ________ .
--- Shenzhen is a beautiful city. --- Yes. You can see a lot of flowers and trees on ________ of the streets .
-- What can trees do _________ us ?--- They can _________ harmful gases and produce oxygen .