The correct option is A Vibrant
The given passage is about a carnival in the capital city of Matsupaa, Maru. The phrase 'rich and colourful' is used to describe the past of Matsu, in terms of its culture. From the options, 'vibrant' means 'lively, exciting', it means the same as 'rich and colourful', colourful also refers to liveliness here, and rich means vivid. Hence vibrant is the most suitable option, and A is correct. 'Wealthy' means 'having great wealth' in the form of money and valuable items, but here it does not mean that, 'wealth' cannot be used to describe the culture, culture is abstract and 'rich and colourful' refers to the richness of the culture, whereas 'wealth' is used for something concrete, like money, hence option B is incorrect. 'Crowded' means 'uncomfortably close together', like a crowded marketplace where there are too many people around, such that it gets uncomfortable. The Matsu past cannot be crowded, hence option C is incorrect. 'Technicolour' means 'vividly coloured', having a lot of colours, but the phrase "rich and colourful" does not refer to something that is coloured, but it speaks of the past of Matsu, the culture. 'Technicolour' describes a concrete noun, something that can be seen, but the "Matsu past" is not a concrete thing, but a period of time, hence it cannot replace the phrase and option D is incorrect.