Unsupervised Learning is the most appropriate for clustering customers based on purchasing behavior. In unsupervised learning, the algorithm identifies patterns and groups data without any predefined labels, making it ideal for clustering tasks like this.

In MongoDB, the FIND command is used to query documents within a collection. It allows you to specify criteria to filter the documents you want to retrieve. MongoDB uses a flexible and powerful query language to find data in collections, making it well-suited for NoSQL document-based data storage.

To prevent data leakage, it's essential to fit a scaler on the training set (Option A) and then apply the same transformation to both the training and test sets. This ensures that the test set remains independent of the training data.

Before deploying a model into production, it's crucial to have a testing phase to evaluate the model's real-world performance. This phase assesses how the model performs on unseen data to ensure its reliability and effectiveness.

The heights recorded as 500 cm are likely outliers in the dataset. Outliers are data points that significantly differ from the majority of the data and may indicate measurement errors or anomalies. It's important to identify and handle outliers appropriately during data analysis.

ARIMA (AutoRegressive Integrated Moving Average) captures both trend and seasonality in time series data. It combines autoregressive, differencing, and moving average components to model complex time series patterns, making it a powerful method for forecasting data with seasonal and trend components.

Seaborn is a Python library built on top of Matplotlib, designed for statistical data visualization. It provides a high-level interface for creating informative and attractive statistical graphics, making it a valuable tool for data analysis and visualization.

The Pooling Layer in a CNN is responsible for reducing the spatial dimensions of the input. This layer downsamples the feature maps, which helps in retaining important features and reducing computational complexity.

HDFS (Hadoop Distributed File System) is the primary component in the Hadoop ecosystem for distributed data storage. It is designed to store large files across multiple machines and provides data durability and fault tolerance.

Text data from social media platforms is typically unstructured. It doesn't have a fixed format or schema. It may include text, images, videos, and other content without a well-defined structure, making it unstructured data.