You are looking to Improve the efficiency of testing.

Context Analysis:

The developers claim many defect reports are invalid. Reviewing defects that are rejected or closed without fixes can highlight issues like incorrect environment setup or missed testing steps.

Evaluation of Options:

A. In the ones that are stuck in the In Progress state:

Incorrect. These defects are still being investigated, not confirmed as invalid.

B. In the ones that are Resolved but not Closed:

Incorrect. These defects have been fixed but not yet verified; they are not considered invalid.

C. In the ones that are in the status Rejected or Closed without a fix:

Correct. Rejected defects are marked invalid and are directly related to the problem described.

D. In the ones with the status of Re-Opened:

Incorrect. Re-opened defects indicate recurring or unresolved issues, not invalid reports.

Syllabus Alignment:

ISTQB highlights analyzing defect statuses to improve defect reporting and management processes (TM-2.3.5).

References:

ISTQB Advanced Level Test Management Syllabus (TM-2.3.5)​