All of my challenges have ( 1 ) being out of my comfort zone in one way or another. But the biggest challenge is ( 2 ) all my friends go home for the winter break on social media while I am thousands of miles away from my family on Christmas.

From Unit 2, we know that the biggest difference between human beings and chimpanzees is one percent difference in DNA.

__________ are generally young or middle-aged women of strong character and refined disposition. Most of them are faithful wives, loving mothers, and pure women from feudal society. ( ) A: Caidan B: Qingyi C: Wudan D: Zhengjing

________ quite recently， most mothers in Britain did not take paid work outside the home.

The toys most boys play with are different from those that girls play with because （） A: their social roles are rigidly determined B: most boys would like to follow their fathers' professions C: boys like to play with their fathers while girls with their mothers D: they like challenging activities