Grain production in the world is(), but still millions go hungry.

单项选择题By the middle of the 21st century, the vast majority of the world's population()in cities rather than in the country.

A. are living
B. will be living
C. have lived
D. will have lived

单项选择题()an answer, she decided to write him another letter.

A. Not having received
B. Not receiving
C. Not received
D. Not being received