已知数列{an}中，a1=1，a2=2+3，a3=4+5+6，a4=7+8+9+_爱下问搜题

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问题选择题

已知数列{a_n}中，a₁=1，a₂=2+3，a₃=4+5+6，a₄=7+8+9+10，…，则a₁₀=（　　）

A．610

B．510

C．505

D．750

答案

答案：C

完形填空

Mary is my friend. Her mother’s birthday is coming. She wants to buy a birthday present her mother. But she doesn’t have money. She can’t buy one. She is very . She thinks and thinks. She has an idea (主意). She can make a present by herself. So she uses a piece of paper a card. On the front, she a beautiful house with some flowers around it. On the back she writes, “To my dearest mummy in the world. I will buy you a real (真的) like this.”
her mother’s birthday, Mary gives her the card. After she sees the card, tears (眼泪) fall down from her face. “ are you crying?” Mary asks, “You don’t like it, right?” “Of course not,” she says, “I love it very much. I because (因为) I am the happiest mother in the world. I have a great . I love you forever.”

判断题

声源一个月内超标不足15天的，噪声超标排污费按月征收。