This is the type of question that should NOT be asked by schools because myself having had an opiate addiction, have found that lots of schools do not teach real facts regarding drugs.
However, D. will get you the correct answer because of our educational system :(
In reality, it is true in some cases but even the wording of "more intense" defeats the purpose of educating the youth about safe usage.
A benzodiazepine and alcohol will have a huge effect as they both affect GABA and will led to respiratory depression when combined (as will opiates).
When you combine some drugs, you can get a wide variety of effects.
This is not just recreational drugs but medication too.
Use pubmed as a good source for pharmacology information
