By the time（或者BY+时间）后面接什么时态?做过很多题,大多数情况下是用完成时,但是我也做过有填进行时的,而

By the time（或者BY+时间）后面接什么时态?做过很多题,大多数情况下是用完成时,但是我也做过有填进行时的,而下面这题答案是C,用了一般将来时,为什么?
By the time this article goes to press,I c my master's degree in hand.
A.would have B.would have had C.will have D.should have
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为什么这里选D？