Explanation
The modeling format that will show the requirements for both systems side by side when performing a gap analysis between two existing systems to combine into a single system or run just one system is a matrix. A matrix is a table that shows the relationships, dependencies, comparisons, or mappings between two or more sets of data or information. A matrix can help to visualize and analyze the similarities and differences between two systems.
The other options are incorrect because:
Option A is incorrect because an activity flow is not a modeling format that will show the requirements for both systems side by side, but a modeling format that will show the sequence and conditions of activities within a system or solution. An activity flow is a graphical representation of the inputs, outputs, triggers, and outcomes of activities within a system or solution.
Option C is incorrect because a glossary is not a modeling format that will show the requirements for both systems side by side, but a modeling format that will show the definitions and descriptions of terms or concepts within a system or solution. A glossary is a repository that contains the meanings, attributes, formats, and relationships of terms or concepts within a system or solution.
Option D is incorrect because a bubble chart is not a modeling format that will show the requirements for both systems side by side, but a modeling format that will show the distribution and correlation of data points within a system or solution. A bubble chart is a graphical representation of data points that vary in size and position according to their values.
References:
BABOK Guide v3, section 10.16: CRUD Matrix
CCBA Exam Questions, question 25