[NTG-context] Conditional Text

Greetings! Is it possible to have parts of the ConTeXt file processed conditionally? I'm hoping to be able to do something like: (in ConTeXt file) Question: What is the derivative of $e^{sqrt{x}}$\\ \some-command-start Answer: $\frac{d}{dx} e^{sqrt{x}} ... $ \some-command-end So that, in the command line, if I run "texexec --pdf quiz01.tex" then it will NOT include the answer section, but if I run "texexec --pdf quiz01.tex -some-other-command" it WILL also include the answer section. I'm confident this can be done through an if or if-defined construct. However, I could not find such commands/macros in the ConTeXt manuals (both the beginners and the detailed manual). Thanks in advance, --tk