What can be used to ignite heat-sensitive explosives such as black powder?

For igniting heat-sensitive explosives like black powder, using flashbulbs is effective because they create a brief but intense burst of light and heat that can ignite the material without prolonged exposure to high temperatures.

Flashbulbs operate by providing a rapid discharge of energy when activated, which can facilitate ignition under circumstances where other methods—such as lighters, matches, or direct flames—might introduce risks of prolonged heat exposure or combustion that could be dangerous for sensitive materials.

Heat-sensitive explosives are susceptible to ignition not just from open flames, which can scorch them and lead to unintentional detonation, but also from too much sustained heat. Since flashbulbs ignite quickly and do not maintain heat, they present a safer alternative.

The other options, while they can ignite certain materials, are less suitable for sensitive explosives due to their potential for prolonged heat application or open flames. Thus, the characteristic of flashbulbs makes them a particularly strategic choice for safely igniting such explosives like black powder.