阅读下列材料：

材料一 ……欲求御外之术，唯有力图自治，修明前圣制度，勿使有名无实；而于外人所长，亦勿设藩篱以自隘，斯乃道器兼备，不难合四海为一家。

——《李鸿章》

材料二 严复说：“及今而图自强，非标本并治焉，固不可也。不为其标，则无以救目前之溃败；不为其本，则虽治其标，而不久亦将自废。”

——《中国近代史》

材料三 日本明治维新政治家、革新家大久保利通说：“英、美、法等国的开化，高我数层，(日本无论如何模仿)也望尘莫及，我认为德、俄两国必有很多东西可以成为我们的准绳。”

——《明治维新史》

材料四 康有为说：“观大地诸国，皆以变法而强，守旧而亡。”……1898年6月16日，光绪皇帝召见康有为，康有为向皇帝提出改革方案：政治方面要求“假日本为向导，以日本为图样”。

——《中国近代史》

请回答：

两条直线相交时有____个交点．两条直线相交成____角时，这两条直线互相垂直．

A

    Skin­diving is a new sport today. This sport takes you into a wonderful new world. It is like a visit to the moon. When you are under the water, it is easy for you to climb big rocks, because you are no longer heavy.

    Here, under the water, everything is blue and green. During the day, there is plenty of light. When fish swim nearby, you can catch them with your hands.

When you have tanks of oxygen on your back, you can stay in deep water for a long time. But you must be careful when you dive in deep water.

    To catch fish is one of the most interesting parts of this sport.

    What's more, there are more uses for skin­diving. You can clean ships without taking them out of water. You can get many things from the deep sea.

    Now you see that skin­diving is both useful and interesting.

不等式组的解集在数轴上表示如图，则该不等式组是（）