题目内容：
17. (阅读理解题)Passage 4Questions 26 to 30 are based on the following passage.
Every country has secret services to help protect it against serious threats from terrorists, major criminals or even from other countries. People who threaten to harm a country always plot in secret, so the intelligence agencies have to work in secret to find out what is being planned before it happens, so that it can be prevented. They do that in many different ways – by secretly listening to their targets talking on the phone, by planting microphones to overhear meetings, by watching the targets as they move from place to place and by recruiting some of the targets to act as double agents to report on what is going on.
For most of my career I worked in one of the UK’s three intelligence services, MIS, the domestic security service. I first joined in the 1970s, in the middle of the Cold War, when the war was divided into two armed camps, the Soviet Union(苏联) and its allies on the one side and Western Europe, America and their allies on the other. The Cold War never became a fighting war. It was an intelligence war, with intelligence officers from both sides trying to find out what the other side was doing, what kind of weapons they had, when and if they might start a war and what their plans were. Both sides were secretly working in each other’s countries.
Nowadays one of the biggest threats to th
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