阅读下面短文，掌握其大意，从每题所给的A、B、C、D四个选项中，选出最佳选项。
It's a small gas station that has snacks, drinks, cigarettes, and candies. The young man behind the counter knows his 1by name and what they usually want to buy. He treats children and adults with equal2He reads science fiction behind the counter when business is3
One day, three people rushed in and grabbed food off the shelves as fast as they could,4not planning to pay for it. He hit the “panic button”, then went over the counter and 5the front door. It was obvious they were homeless, and equally obvious that they weren't going6with the food. They7the food and simply crowded together in panic— knowing the police were8 the way.
Imagine what they must have felt like when they were told they didn't have to steal if they were that9“We have food in the back, expired (到期) but still 10to eat. If you need food, you11have some.”
They were told to12what they had dropped and put it back, and then asked to sort out the mess. They were doing just that13the police arrived. The officers were told the situation was under control and the police were no longer14.
This wasn't what they had 15.They were being treated as human beings who could right the wrong they'd done. Shocked, they quickly followed orders to take turns and use the restroom to clean up themselves.
Soon three 16people walked out with all the17their arms could hold. They were18that, if they needed to come back again, they were to ask and not just grab.
And then the young man went back to read until the next customer came in. He would be the 19 person in the world to say he was a hero. But he gave three people something they were badly in need of —a20 amount of self-respect and a little bit of hope.
X、Y、Z、W为四种短周期主族元素。其中X、Z元素原子的最外层电子数相同，W与X、Y既不同族也不同
周期：X原子最外层电子数是核外电子层数的3倍；Y的最高正价与最低负价的代数和为6。下列说法一定正确的是