- What do you like? - I like biscuits.

如图，航拍无人机从A处测得一幢建筑物顶部B的仰角为30°，测得底部C的俯角为60°，此时航拍无人机与该建筑物的水平距离AD为90米，那么该建筑物的高度BC约为____米．（精确到1米，参考数据： $\sqrt{3}$ ≈1.73）

写出下列中溶液中的溶质的化学式，并指明溶液的颜色

澄清石灰水____ （____ ）色；　硫酸铜溶液____ 　（____ ）色；盐酸　____ （____ ）色；“稻花香白酒”____ 　（____）色；硫酸亚铁溶液　____ （____ ）色；氯化铁溶液____ （____ ）色．

    For thousands of years, people have used plants to make medicines. They used different parts of the plants —the roots, the leaves, the flowers, and the bark (树皮). Today, doctors have rediscovered more medicinal (药用) values of some plants. Let's look at some examples.
    Foxglove is a common plant. People have used it to make the heart slow down. Recently scientists have developed another drug from it. This new drug helps prevent other heart problems.
    In some areas, malaria has been a problem. Scientists have learned that the bark of a South American tree, the cinchona, can be made into a drug to prevent malaria. For a long time, the Chinese have known that a special plant, wormwood, can also fight malaria. Scientists have been working with it to develop new drugs against malaria.
    In Germany, some scientists studied garlic (大蒜) for four years. They found that it helps prevent the build-up of plaque (血小板) because too much plaque is bad for health. This very common plant continues to be studied.
    As we know, there are about 250,000 kinds of flowering plants in the world. Scientists have only studied little more than one percent of plants for their medicinal value. Maybe medicines for AIDS and cancer will be made from the other 99 percent.