题目

阅读理解If you bought some bread months ago but never ate it, how can you tell whether it is still safe to eat?The common way is to check the use－by date. If that date has already passed, you're likely to throw the bread away. But is that really necessary?According to a new report from the US Natural Resources Defense Council (NRDC), tons of food is wasted each year, largely because people don't fully understand what use－by dates actually mean.Food dating was introduced in the 1970s because consumers wanted more information about the things that they were eating. When they first showed我们生活在一个不断变化的物质世界里。下列属于化学变化的是A.镁条燃烧B.试管破裂C.汽油挥发D.水结成冰