Martin is a fifteen-year-old boy. He used to be a“problem child”, but a recent1with his mother changed his life. He didn't use to give his mother many problems.2, after his father's death a few years ago, Martin's life became3more difficult. His mother couldn't afford to pay for her child's education. To do this, she4work, and so was often not at home.

    His mother looked after him as5as she could. Unfortunately, Martin still caused problems. He was not6in studying and he often got in to trouble. Luckily, his mother was very7and didn't give up trying to help him. In the end, she8a difficult decision:to send him to a boys' boarding school. Martin hated it and used to cause a lot of trouble.

    One day, he told his teacher he wanted to leave the school. The teacher said it was necessary for Martin to9with his mother. Martin called his mother, but to his10, this phone call changed his life. “It was exactly11ineeded,”he said. “My mother helped me to understand how much she had given me. She also told me that even though my father was no longer with us, he was12me and would always take pride in every thing good I do. That's when I decided to change. I realize that13my father died, I have been afraid of being alone, and have tried to make my mother pay more attention to me. ”

    Now Martin has14changed. He has been working hard and is now one of the best students in his class. How was he able to change?His mother's15helped him to feel good about himself.

在等差数列$\left\{a_n\right\}$中，$3\left(a_3+a_5\right)+2\left(a_7+a_{10}+a_{13}\right)=48$,则等差数列$\left\{a_n\right\}$的前13项的和为（   ）

世界上最大的大陆是(      )