在一棵树的10m高处有两只猩猩，其中一只爬下树走向离树20m的池塘，而另一只爬到树顶后直扑池塘。如果两只猩猩经过的距离相等，问这一棵树有多高？

在欧洲人看来，“它意味着启蒙运动的思想是切实可行的——一个民族有可能建立一个国家，有可能制定一种建立在个人权利基础上的切实可行的政体”。于是，这个的国家“成为自由和机会的一个象征，作为一块新的、没有历史负担和枷锁的大陆而受人羡慕”。这里说的“这个国家”指的是（　　）

    Whether you have a piece of land or a few pots on a balcony, plant a family garden: You'll all live healthier! Gardening is an easy activity to share and you'll harvest benefits along with your fresh vegetables, colorful flowers, and aromatic herbs. Even better, you don't have to wait for your plants to bloom to see those benefits.

    When parents and kids work together to plant and care for a garden, they can all enjoy these benefits:

    Physical activity: Gardening and yard work are mild exercise, which we all need every day (for at least 30 minutes). While tending your family garden doesn't require the intense activity of running or playing singles tennis, it's still beneficial to your health. For one thing, research shows that once you start gardening, you usually continue for more than 30 minutes. And gardening combines delicate skill strengthening and stretching.

    Lower stress, better mood: Gardening is excellent stress relief for good reasons: enjoying fresh air and sunlight, performance of relaxing tasks, and even contact with harmless bacteria in the soil that helps release serotonin (血清素) in the brain.

    Outdoor time: Children prefer spending a lot of time indoors, which can negatively affect their behavior and health. A family garden gets them outside enjoying and experiencing the natural world.