I also disagree with this. There must be a difference between thinking you are having a mystical experience and actually having one...
I think you misunderstood.
If you truly believe you are having a mystical experience then in all probability you are having one. This doesn't mean that you can evoke one by simply thinking about having one.
B is and always will be the correct answer !
Who made you the minister of correct answers?
There is no objective truth, only 6 billion subjective ones. Your truth may not be my truth or your friend Harry's truth.
Scientific and spiritual views do not necessarily need to be in any opposition to each other. They can coexist.
To my knowledge, so far no one has researched the absolute composition of psychedelic mushrooms. We only know of the alkaloids which we have found in them, which certainly are
mostly responsible of the effects from them.
But, how then do you explain the clear differences in effect between different mushroom species, or the differences in effect between pure synthetic psilocin and psilocin containing mushrooms?
There might be lots of so far unknown substances in the mushrooms which in combination with the most active alkaloids contribute to the subjective effects of the mushrooms. No one knows for sure, yet.
There are so many things we don't understand about fungi. They could very well be sentient beings, no one has scientifically disproven this yet. We also don't fully understand how the human consciousness works. Best would be not to make too many hasty assumptions at this point.