A Radiation Reality Check
关于辐射的真相
The source of radioactivity is an atom so obese that it defies the laws of attraction gluing together our material world and spits out little pieces of itself -- two kinds of particles and a stream of gamma rays, similar to X-rays. An overdose of gamma rays is like a vicious sunburn, with skin damage and elevated cancer risks, but those particles are too big to penetrate our skin, meaning that they need to be swallowed or inhaled to wreak damage. The truly fearful event in a nuclear accident, then, isn't fallout but meltdown, where the core burns through the floor and suffuses the water table. There it causes agricultural havoc and radioactive dust that you better not breathe. We're not dropping dead all together from radiation poisoning or its ensuing cancers on a daily basis because, like all poisons, it isn't the particular atom that will get you. It's the dose. And damage from radioactivity requires a much greater dose than any of us would have believed.
问题：According to the passage what ultimately causes the death of the human being ?
(A) The vicious gamma rays
(B) The quantity of radioactivity
(C) The radioactive dust
(D) The meltdown in a nuclear accident
附加一个写作小句子：
But there is, in all this, some good news.
词汇突破(一定仔细看) ：
1. All together = en masse
2. on a daily basis = everyday
3. ensuing 随后的
4. havoc= mayhem 灾难
5. obese 庞大
6. vicious 这里理解为：恶性的
放射性产生的根源是一个太庞大的原子违背了万有引力定律(我们物质世界存在的基本原理)并发生分裂，释放出两种粒子和一束类似于X光的γ射线。过量暴露在γ射线中就好像恶性晒伤一样，会造成皮肤损伤并提高罹患癌症的风险，但由于粒子的体积太大，所以它们无法穿透我们的皮肤，也就是说这些粒子要被人类吞入或吸入才会造成损伤。核事故中真正可怕的不是放射性尘埃而是堆芯熔毁，堆芯熔毁能够烧穿地表并渗入地下水。堆芯熔毁可以带来农业灾害和不宜吸入的放射性尘埃。人类不会因为放射性毒害或由此引发的癌症而每天大量死亡，这是因为与所有的有毒物质一样，罪魁祸首不是特定的原子，而是剂量。放射性造成损伤所需的剂量远远超过我们通常认为的水平。
来源：新东方在在线论坛