如图为两个物体A和B在同一直线上沿同一方向同时做匀加速运动的v﹣t图线，已知在第3s末两个物体在途中相遇，则下列说法正确的是（   ）

Good morning.

D

    How old is "old"? The answer has changed over the years. Two Hundred years ago, you were old at 35. At the beginning of the 20th century, the average life span(平均寿命) was 45. In 1950, 70-year-olds were really old. Today, a healthy 70-year-old is still thought young.

    So, how old is "old"? The answer is one you've heard many times, from all kinds of people. "You are as old (or young) as you feel. " Your age simply tells you how many years you have lived. Your body tells you how well you've lived.

    "Nobody grows old by living a number of years, "Wrote a writer. "People grow old when they don't have their ideals(理想)." People shouldn't have the wrong ideas about aging. Sometimes, older minds can be as bright as young minds. Alice Brophy once said, "It makes me unhappy when people say, 'You look young for your age.' What does that mean? You know you can die old at 30 and live young at 80."

实验室制取气体的常见装置如图所示，回答下列问题：

（1）标号a的仪器名称为____ ；

（2）利用AE装置组合制取氧气，反应的化学方程式为____ ．实验过程中，发现收集的氧气不纯，可能的原因是____ （写一点），从燃烧条件分析，加热过程中试管内的棉花没有燃烧的原因是____ ．

（3）实验室制取二氧化碳的药品为____ （写名称，下同）和____ ，制取二氧化碳的装置组合为　____ （填标号）；该装置还能制取氧气，反应的化学方程式为　____ ．