题目内容：

Even when you’re extremely busy, you aren’t using your time with 100% efficiency. There are gaps in everyone’s schedule where they aren’t doing anything important. Even if your schedule has no gaps, there is probably lots of time where you aren’t working as fast or as effectively as you possibly could.

Why aren’t you completely efficient? It’s because time isn’t the limiting factor. If it were the limiting factor, people could work non-stop without breaks or any unproductive distractions. Instead, people, even those who are highly productive, need to take breaks, occasionally procrastinate(拖延) and slow down on tasks throughout the day.

The real and most important limiting factor for productivity is your energy levels to pay attention. Energy levels limit your productivity because when you’re tired, you can have ample time and still not get everything done. Your attention ability is also limited, because even if there are a million things that need to be done, you can only focus on one or two at a time.

You might not be able to insert another 4-5 hours into your schedule without making some sacrifices. But even extremely busy people can add an hour or two into their schedule without cancelling anything. The reason it’s hard to “find time” isn’t a lack of time. It’s because you don’t have enough energy left to focus on something else that needs to fit into your day.

I first suspected time wasn’t the real problem during an extremely busy period in my life over a year ago. I was insanely busy, but at that time I still exercised regularly. I had daily-to-do lists with over twenty items, and I still found time to exercise. However, after a few weeks off, due to illness, stopped exercising. I was not busy by any standards, in fact, my schedule was incredibly light. Despite this free time, I found it hard to find time to exercise. It seemed to get pushed later and later into my schedule until it was gone. How can I explain this odd experience? I believe you have known it.

1.If someone can’t work with 100% efficiency, the most important limiting factor is ______.

A. a schedule without gaps           B. breaks and distractions

C. the limited time                  D. the limited energy

2.According to paragraph 4, everyone, including the extremely busy people, can ______.

A. work without any rest

B. focus on many things at a time

C. find some more time in a day

D. do some exercise regularly

3.After a few weeks off, what was the change of the writer’s life?

A. He had a longer daily to-do lists with over twenty items.

B. He stopped doing exercise because of the lack of energy.

C. He found it hard to find time to exercise because he was busier.

D. He pushed most of the things later and later in his schedule.

4.The writer gives the example of himself in the last paragraph in order to ___________.

A. prove what the real limiting factor is

B. show us how busily he needs to work

C. explain how important a healthy body is

D. tell us what an odd experience he has