We shall probably never be able to __________ the exact nature of these sub-atomic particles.

单项选择题The financial problem of this company is further __________ by the rise in interest rates.

单项选择题The medicine __________ his pain but did not cure his illness.

单项选择题It was __________ that the restaurant discriminated against black customers.

单项选择题Professor Hawking is __________ as one of the world's greatest living physicists.

单项选择题Which of the following is true of the ethnic minority families in the U. S. according to the passage（）

A．Their cultural patterns are usually more adaptable.
B．Their cultural concepts are difficult to comprehend.
C．They don't interact with each other so much as White families.
D．They have closer family ties than White families.