训练要求：下面的短文有15处空白，请根据短文内容为每处空白确定1个最佳选项。
One Good Reason to Let Smallpox Live It’s now a fair bet that we will never see the total extinction(灭绝) of the smallpox(天花) virus. When smallpox was completely got rid of in the world, scientists wanted to ____ (51) the killer virus in the last two labs—one in the US and one in Russia. They asked: If smallpox has truly gone from the planet,____(52) point was there in keeping these reserves? In reality, of course, it was naive to ____ (53) that everyone would let go of such a powerful potential weapon. Undoubtedly several nations still have ____(54) vials (小药瓶). And the last “official” stocks of live virus bred mistrust of the US and Russia, ____(55) no obvious gain. Now American researchers have ____ (56) an animal model of the human disease, opening the ____ (57) for tests on new treatments and vaccines (疫苗). So once again there’s a good reason to ____(58) the virus---just in ____(59) the disease puts in a reappearance. How do we ____ (60) with the mistrust of the US and Russia? _____(61). Keep the virus ____(62) international support in a well-guarded UN laboratory that’s open to all countries. The US will object, of course, just as it ____(63) a multilateral (多边的) approach to just about everything. But it doesn’t mean the idea is ____(64). If the virus is useful , then let’s ____ (65) it the servant of all humanity ---not just a part of it. 51