A code coverage of 80% is not sufficient to ensure that the code is free of defects. While having a test plan for each sprint is a good practice, it is not enough to reduce the number of defects if the test plan is not comprehensive enough. The following recommendations can help reduce defects:

B. The code coverage should be increased to 95%: By increasing the code coverage, it ensures that a higher percentage of the code is tested, which in turn reduces the risk of defects. The additional tests will help identify issues earlier in the development lifecycle, making them less costly to fix.

D. The acceptance criteria should have more details: Acceptance criteria define the conditions that must be met for a story or feature to be considered "done." If the acceptance criteria do not provide sufficient details, it can lead to misunderstandings and gaps in testing, which can result in defects. By providing more detailed acceptance criteria, it ensures that the requirements are better understood and that the testing is more comprehensive.

Option A (The test script should be used to define the test classes) is not a recommended approach. While the test script can be used to define the test cases, it is not sufficient to ensure that the tests cover all scenarios and edge cases. It is also not clear if the issue is related to the quality of the test cases or if there is a need for more comprehensive testing.

Option C (The test analyst who creates the test plan must also create the test classes) is not a recommended approach either. While having the test analyst create the test classes may ensure that the test cases are more comprehensive, it is not necessarily the best use of the test analyst's time. It is also not clear if the issue is related to the quality of the test cases or if there is a need for more comprehensive testing.
A,D...