Explanation
A testing design technique based in the system requirements. Decision table testing is a black-box testing technique that is used to test complex business rules or logic that involve multiple conditions and actions.
Decision table testing uses a tabular format to represent all possible combinations of inputs (conditions) and outputs (actions) for a given decision. Decision table testing helps to ensure that all scenarios are covered and tested. A detailed explanation of decision table testing can be found in A Study Guide to the ISTQB Foundation Level 2018 Syllabus, pages 47-511.

The statement that component testing tests interfaces between modules and interactions of different parts of a system does not describe component testing. Component testing is the process of testing individual software components that are separately testable, such as modules, programs, objects, classes, etc. Component testing verifies the functionality and quality of the components in isolation from other components. Component testing does not test the interfaces or interactions between components, as this is done in integration testing.
References: Certified Tester Foundation Level Syllabus, Section 5.1.2

Explanation
To be based on an analysis of the structure of the component or system. White box testing techniques are based on the internal structure and code of the system, not on its specifications or functionality. White box testing techniques include statement coverage, decision coverage, branch coverage, path coverage, etc. White box testing techniques are usually performed at lower levels of testing, such as unit testing or component testing. A detailed explanation of white box testing techniques can be found in [A Study Guide to the ISTQB Foundation Level 2018 Syllabus], pages 68-74.

Explanation
State transition testing is a technique that uses state transition diagrams as a test basis to derive test cases2. A state transition diagram shows the states of a system and the transitions between them triggered by events or conditions2. A test case can cover one or more state transitions, depending on the test objective and coverage criterion2. In this question, the test cases (i) and (ii) cover different sets of state transitions, as shown below:
Test Case
State Transitions
(i) X-Z-V-W
S1 - S2 - S3 - S4 - S2
(ii) W-Y-U-U
S4 - S2 - S4 - S4 - S4

The statement that best characterizes maintenance testing is A. Maintenance testing is triggered by changes to delivered software and uses impact analysis to minimize the amount of regression testing needed. Maintenance testing is a type of testing that is performed on a software product after it has been delivered to the customer or user, and aims to ensure that the software product still meets its requirements and expectations after any changes or modifications. Maintenance testing is triggered by changes to delivered software, such as bug fixes, enhancements, patches, updates, etc., and uses impact analysis to determine the scope and extent of regression testing needed. Impact analysis is a technique that analyzes the potential effects of changes on the existing software product and its components, dependencies, interfaces, etc., and identifies which parts of the software product need to be retested or modified. Impact analysis helps to minimize the amount of regression testing needed by focusing on the most affected or critical parts of the software product. A detailed explanation of maintenance testing can be found in [A Study Guide to the ISTQB Foundation Level 2018 Syllabus], pages
81-82.