Answer: A. run away from it
The African black mamba is the fastest moving land snake at 16-20 km/h. A person—regardless of how scared they are—could easily escape and outpace that snake with no problem. In reality, there's no need to run at all. The snake won't attack you unless you provoke it (i.e., don't do what option B, C, or D suggests), and snakes are probably more scared of us than we are of them. If I could add an option, I'd add: E. Leave it alone or keep still. If it moves towards you, slowly back off, and if it moves again, keep still, and then move slowly. The snake will eventually back off unless you do something to agitate it.
