Health is something we tend to ignore when we have it. When our body is doing well, we are hardly (26) ______ of it. But illness can come, even when we are young. In fact, childhood has been a very susceptible time. Many diseases attack children in particular, and people know very little how to cure them once they (27) ______. The result was that many children died. About a century ago, (28) ______, scientists found out about germs, and then everything changed. The cause of many diseases was found, and cures were developed. As this medical discovery spread, the world became much safer for children. The result is that whereas a hundred years ago, the average man lived for 35 years, nowadays, in many areas of the world, people can expect to live for 75 years. And what do we expect by the year 2020? (29) ______, medical science will continue to advance. Some people will be able to avoid medical problems (30) ______ are unavoidable today.