In the Optimized Design Experience, Data Analyzer is a new tool that replaces Explorer. Data Analyzer allows you to quickly create ad hoc analysis based on models or datasets. You can use Data Analyzer to explore data, create charts and tables, apply filters and calculations, and save your analysis as stories. Data Analyzer is similar to Explorer, but with some enhancements and new features, such as:
Support for both models and datasets
Support for planning models
Support for story calculations
Support for linked analysis
Support for responsive pages
Therefore, the correct answer is Data Analyzer, as it is the tool that replaces Explorer in the Optimized Design Experience