Lin Xiao, 21, a student at Guangdong University, has a big family - her two parents, a younger brother and two younger sisters. Lin took her role as the "big sister" seriously. When her first sister was born, Lin took turns with her mom holding the baby late into the night. "I almost did everything that was supposed to be a parent's job, but I felt proud of myself," she said. Not all of Lin's classmates shared her experiences because of the family planning policy , a law that was carried out in China about forty years ago. But the situation is about to change. A new policy made on October 29 said all couples can now have two children. The new policy is expected to help raise the population of China. Recently, China has been facing an aging population and labor shortages because of the low birth rate . The two-child policy may also be the gift for every only child. Researchers found that growing up with a brother or sister can have good influence on one's mental health. "Brothers and sisters do matter in unique ways. They give kids something that parents don't." Laura Walker, a professor from Beijing University, told China Daily. She noted that having a brother or a sister protects teenagers against loneliness, fear and so on. Liu Fang, 20, from Shenzhen University, has a 2-year-younger sister. When her sister disagreed with parents over choosing a college major, she helped her to communicate with parents. "If necessary, I would always have her back," said Liu. "The best part of having a sister is that you have a partner, friend and supporter throughout your life." But children with brothers or sisters also have to learn to understand and look after each other, said Laura. The one-child policy caused some problems except _ . A) the aging population B) labor shortages C) the population growth D) the low birth rate
The answer to this question is:
C