Test techniques are methods or procedures that can be used to design, execute, or evaluate test cases. Test techniques can be classified into two categories: specification-based and structure-based. Specification-based test techniques, also known as black-box test techniques, are based on the requirements, specifications, or expectations of the system under test. They do not require any knowledge of the internal structure or implementation of the system. Some examples of specification-based test techniques are use case testing, state transition testing, decision table testing, etc. Structure-based test techniques, also known as white-box test techniques, are based on the code, architecture, or design of the system under test. They require some knowledge of the internal structure or implementation of the system. Some examples of structure-based test techniques are control flow testing, data flow testing, branch testing, statement testing, etc. You can find more information about test techniques in A Study Guide to the ISTQB Foundation Level 2018 Syllabus, Chapter 41.

Explanation
It is not allowed as organizations can't change the test levels as these are chosen on the basis of the SDLC (software development life cycle) model. The V-model is a type of SDLC model that defines four test levels:
component testing, integration testing, system testing, and acceptance testing. Each test level corresponds to a development phase in a parallel manner. Integration testing is an essential part of the V-model, as it verifies that the components work together correctly and consistently2 explains this as follows:
The V-model is a graphical representation of a systems development lifecycle. It is used to produce rigorous development lifecycle models and project management models. The V-model falls into three broad categories, the German V-Modell, a general testing model and the US government standard.
The V-model summarizes the main steps to be taken in conjunction with the corresponding deliverables within project execution and delivery. It describes software development activities from requirements specification to maintenance.
The V-Model demonstrates the relationships between each phase of the development life cycle and its associated phase of testing.
A, C, and D are incorrect answers. A implies that integration testing is not an important test level and can be dispensed with, which is not true as integration testing ensures that the system functions as a whole and meets its requirements. C implies that organizations can decide on which test levels to do depending on the context of the system under test, which is not true as test levels are determined by the chosen SDLC model and its objectives. D implies that integration testing is a very important test level and ignoring it means definite poor product quality, which is true but not relevant to why it is not allowed to do away with integration testing in a V-model.

Explanation
For the code fragment given below, one test case is required for statement coverage and two test cases are required for branch coverage. Statement coverage requires that every executable statement in the code is executed at least once. Branch coverage requires that every possible outcome of each decision point in the code is executed at least once. The following table shows how to achieve statement and branch coverage for the code fragment:
Test Case
Input
Output
Statement Coverage
Branch Coverage
1
x = 3
y = 9
S1, S2, S3
T1 = true
2
x = 5
y = 25
S1, S2
T1 = false
As shown in the table, test case 1 covers all three statements (S1, S2, S3) in the code fragment, achieving
100% statement coverage. Test case 2 covers only two statements (S1, S2) in the code fragment, but it exercises a different outcome of the decision point T1 (if x < 4), achieving 100% branch coverage.