--- May I visit you at 10 o’clock tomorrow morning?--- I’m afraid I ______ a document for my boss then. What about 12:00?
As the immune system weakens, it loses the ability ________ illnesses.
My mother went to the private school in person ________ that I would be safe there.
China is expected to export 1 billion mobile phones this year, ________ by a surge in demand for smartphones worldwide.
Misunderstandings ________ from lack of social communication, unless ________ properly, may lead to serious problems.
The text is too difficult. The explanation of our teacher will help make it easy ________.