People from all over the world make friends____ writing letters. One way to find a pen friend is to ____ a club. International Pen Friends started in 1967 and has over 300,000members(成员) in different countries. Their____ member is eight years old, and their oldest member is over 80. Some people write to find out about life in another country, ____ want to practice their English, or enjoy their hobbies. Stamp collectors, for example, write to people in different countries ____ that they can collect the stamps on the letters they receive. Most people just enjoy making friends, and they invite their pen friends to visit them.

My aunt asks me whether I like a woolen sweater       a cotton one.

有关图中地理分界线的说法，正确的是（）

已知甲溶液遇石蕊溶液变红．请回答下列问题：

正四棱锥的顶点都在同一球面上，若该棱锥的高为4，底面边长为2，则该球的表面积为（　　）