题目

In our life, we have rarely expressed our gratitude to the one who'd lived those years with us．In fact, we don't have to wait for anniversaries to thank the ones close to us —the ones so easily overlooked．If I have learned anything about giving thanks, it is this: give it now! While your feeling of appreciation is alive and sincere, act on it．Saying thanks is such an easy way to add to the world's happiness．        Saying thanks not only brightens someone else's world, it brightens yours．If you're feeling left out, unloved or unappreciated, try reaching out to others．It may如图为查德威克实验示意图，由天然放射性元素钋（Po）放出的A射线轰击铍时会产生粒子流A，用粒子流A轰击石蜡时会打出粒子流B，经研究知道(        ) A．A为中子，B为质子 B．A为质子，B为中子 C．A为γ射线，B为中子 D．A为中子，B为γ射线