Hi willwants170!
You comment,
On most strongly supported questions, the correct answers can be fully supported, without a shadow of a doubt, like MBT.
Yes, but rather than considering must strongly supported questions to be "like" MBT questions, it's best to think of them just as MBT questions. And on MBT questions, the answer choice is fully supported by the stimulus, rather than only being highly likely based off of it.
Here, answer choice (B) is fully supported by the stimulus. It must be the case that "[j]ury decisions in cases involving expert witness testimonies are not always determined by the reliability of those testimonies," because we're told in the stimulus that juries frequently are unable to assess the reliability of expert testimonies. If they're frequently not able to assess the reliability of such testimony, then in at least some cases involving expert witness testimony, jury decisions are not determined by the witness's reliability.