1. (2023高三下·成都开学考) 阅读下列短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。

For those who can stomach it, working out before breakfast may be more beneficial for health than eating first, according to a study of meal timing and physical activity.

Athletes and scientists have long known that meal timing affects performance. However, far less has been known about how meal timing and exercise might affect general health.

To find out, British scientists conducted a study. They first found 10 overweight and inactive but otherwise healthy young men, whose lifestyles are, for better and worse, representative of those of most of us. They tested the men's fitness and resting metabolic (新陈代谢的) rates and took samples of their blood and fat tissue.

Then, on two separate morning visits to the scientists' lab, each man walked for an hour at an average speed that, in theory should allow his body to rely mainly on fat for fuel. Before one of these workouts, the men skipped breakfast, meaning that they exercised on a completely empty stomach after a long overnight fast (禁食). On the other occasion, they ate a rich morning meal about two hours before they started walking.

Just before and an hour after each workout, the scientists took additional samples of the men's blood and fat tissue. Then they compared the samples. There were considerable differences. Most obviously, the men displayed lower blood sugar levels at the start of their workouts when they had skipped breakfast than when they had eaten.

As a result, they burned more fat during walks on an empty stomach than when they had eaten first. On the other hand, they burned slightly more calories, on average, during the workout after breakfast than after fasting.

But it was the effects deep within the fat cells that may have been the most significant, the researchers found.

Multiple genes behaved differently, depending on whether someone had eaten or not before walking. Many of these genes produce proteins that can improve blood sugar regulation and insulin (胰岛素) levels throughout the body and so are associated with improved metabolic health. These genes were much more active when the men had fasted before exercise than when they had breakfasted.

The implication of these results is that to gain the greatest health benefits from exercise, it may be wise to skip eating first.

1. （1） The underlined expression "stomach it" in Paragraph 1 most probably means "______".

   A . digest the meal easily B . manage without breakfast

   D. eat whatever is offered

   C . decide wisely what to eat
3. （2） Why were the 10 people chosen for the experiment?

   A . They had slow metabolic rates. B . They could walk at an average speed. C . Their lack of exercise led to overweight. D . Their lifestyles were typical of ordinary people.
5. （3） What happened to those who ate breakfast before exercise?

   A . They successfully lost weight. B . They burned more fat on average. C . They consumed a bit more calories. D . They displayed higher insulin levels.
7. （4） What could be learned from the research?

   A . Too much workout often slows metabolic rates. B . Lifestyle is not as important as morning exercise. C . Physical exercise before breakfast is better for health. D . A workout after breakfast improves gene performances.