Solution

Customer complaints in text form, such as emails and social media posts, fall under unstructured data. This format lacks a fixed organizational framework, making it difficult to store in a tabular or relational database without transformation. Text data requires advanced techniques, like natural language processing (NLP), to extract insights, as it doesn’t follow a pre-set structure like structured data or partially organized format like semi-structured data. Organizations typically use big data tools to manage and analyze unstructured data due to its complex nature. Option A is incorrect as structured data has predefined fields and is unsuitable for raw text data. Option B is incorrect because semi-structured data has some inherent organization (like JSON or XML) which doesn’t fit plain text. Option D is incorrect because relational databases handle structured data well, but unstructured data requires different tools. Option E is incorrect since numerical data lacks relevance to raw textual information.