What are the conditions necessary for static arc ignition?

The conditions necessary for static arc ignition indeed include multiple specific factors, making option B the correct choice. Static arc ignition occurs when a static discharge generates sufficient energy to ignite a combustible mixture. The five critical conditions typically include:

1. Accumulation of static electricity - This can occur through various mechanisms, such as friction between two surfaces.

2. A discharge path - This is required for the static electricity to reach a point where it can generate an arc.

3. The presence of a fuel source - This could be a vapor, gas, or dust that can be ignited.

4. An oxidizer, typically oxygen in the air, which supports combustion.

5. Proper mixture and proportions between fuel and air to facilitate ignition.

Only when these elements come together can a static arc lead to ignition. The presence of just a spark near combustible material, as suggested in another option, may not necessarily lead to ignition without the presence of fuel and proper conditions for combustion. Similarly, high humidity and wind speed or merely the presence of water and solid fuel do not comprehensively address the specific requirements for static arc ignition, as all these factors can influence but do not directly cause ignition without the essential conditions outlined.