The ISTQB CT-AI syllabus indicates inSection 5.2 -- AI for Testingthat AI-generated test cases may not come withpredefined expected results. This is because test-case generation methods---such as evolutionary algorithms, reinforcement learning, or clustering-based sampling---produceinputs, but the tester must still determine the correct outputs. Therefore, OptionCis correct: expected results may not be available, especially when AI produces novel or previously unseen input combinations.

Option A is incorrect: AI-based test generation can improve coverage by exploring large input spaces. Option B is incorrect because the need for oracles does not depend on whether the test case is AI-generated. Option D is incorrect because the syllabus allows using a model as an oracle inback-to-back testing, provided limitations are understood.

Therefore,Option Cis the correct syllabus-aligned statement.