修改程序和数据应实行他人检查，（）操作制，并在（）或晚间进行。

It’s nice to see you again. What_________ since we last met?

A．have you done

B．had you done

C．have you been doing

D．did you do

工程网络计划中，某项工作拖延的时间超过其自由时差，则( )。

A．必定影响紧后工作的最早开始

B．必定影响总工期

C．必定影响紧前工作的最早完成

D．对其后续工作无影响

If those "mad moments"—when you ’can’t remember what your friend has told you or where you left your keys—are becoming more frequent, mental exercises and a healthy brain diet may help.

Just as bodies require more maintenance with the passing years, so do brains, which scientists now know show signs of aging as early as the 20s and 30s. "Brain aging starts at a very young age, younger than any of us had imagined and these processes continue gradually over the years," said Dr. Gary Small, the director of the Center on Aging at the University of California, Los Angeles. "I’m convinced that it is never too early to get started on a mental or brain-fitness program," he added.

In his book, The Memory Bible, the 51-year-old neuroscientist (神经学家) lists what he refers to as the 10 suggestions for keeping the brain young. They include training memory, building skills, reducing stress, mental exercises; brain food and a healthy lifestyle. It’s a game plan for keeping brain cells sparking and neural networks in perfect shape.

"Misplacing your keys a couple of times don’t mean you should start labeling your cabinets. Memory loss is not an inevitable consequence of aging. Our brains can fight back," he said.

Small provides the weapons for a full-scale attack.

Simple memory tests give an indication of what you are up against and tools such as "look" and "connect" are designed to make sure that important things such as names and dates are never forgotten. "So if you wanted to learn names and faces, for example, you meet Mrs. Beatty and you notice a distinguishing facial feature, maybe a high eyebrow," said Small. "You associate the first thing that comes to mind. I think of the actor Warren Beatty so I create a mental picture of Warren Beatty kissing her brow."

Small admits it may sound a bit strange but he says it works. "Mental exercises could be anything from doing crossword puzzles and writing with your left hand if you are right handed or learning a language. It could be anything that is fun that people enjoy doing," he added.

He also recommends physical exercise, a low-fat diet and eating foods rich in fatty acids, such as fish, nuts, and fruits and vegetables high in antioxidants (抗氧化剂) including blueberries and onions in addition to reducing stress.

In this passage, the author mainly tells us().

A. everyone has bad memories sometimes no matter how old he is

B. we can prevent our mind from aging with various methods

C. brain aging starts at the time when we are in the 20s and 30s

D. memory lost is not the sign that we are getting old

读《少年爱因斯坦》课文，回答下列问题：

⑴你对少年爱因斯坦做的哪件事印象最深？

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⑵爱因斯坦小时候学习的最大特点是什么？

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请简述QTFJ型切缝机缝边时连续打折的主要原因。