This is Part 6 of Reading and Use of English: paragraphs have been removed from a long text, and you put each one back in the right gap. There's one more paragraph than there are gaps, so one fits nowhere.
It tests how well you understand the structure of a text: how the story or argument develops, and how each part links to its neighbours through reference words, linking words and topic.
Before looking at the options, read the main text from start to finish. You need its overall line, the order of events or the steps of the argument, because a gap is sometimes explained by a whole paragraph rather than a single sentence.
Look at the end of the text before the gap and the start of the text after it. The missing part has to connect both ways: it picks up the idea that closes the previous section and leads into the one that follows.
Mark names, places and reference words such as 'this', 'these', 'such', 'the latter', 'he', 'there' or 'at that time'. A 'this' at the start of an option needs a clear partner just before the gap; without one, it doesn't belong there.
Notice linkers and time expressions in the options and in the text: 'however', 'even so', 'as a result', 'later', 'by then', 'eventually'. They show whether a part contrasts, continues or moves things on, and they must fit the order of events.
Each paragraph usually develops one main point. Sum up each one in a few words, then see which missing part bridges the gap between two of them. Repeated vocabulary and synonyms of key words are strong signs you're right.
The extra option shares the topic and often the vocabulary of the text, so it always looks possible. If an option seems to fit two gaps, or a gap seems to take two options, test the reference and grammar links again before deciding.