As the immune system weakens, it loses the ability ________ illnesses.
A．fighting B．fought
C．to fight D．to be fought
My mother went to the private school in person ________ that I would be safe there.
A．confirming B．having confirmed
C．to confirm D．confirmed
China is expected to export 1 billion mobile phones this year, ________ by a surge in demand for smartphones worldwide.
A．drive B．driving C．to drive D．driven
Misunderstandings ________ from lack of social communication, unless ________ properly, may lead to serious problems.
A．arisen; handling B．arising; handled
C．rising; handled D．risen; handling
The text is too difficult. The explanation of our teacher will help make it easy ________.
A．to understand B．to be understood
C．understood D．understanding
It is said that sixty percent of all energy ________ in the world today is being lost as waste heat.
A．produced B．producing
C．to produce D．having produced
