1. A. Restrictive
The information about striking in a dry forest is necessary for the rest of the sentence. If the lightning struck a lake, it wouldn't cause a forest fire. This specificity of where the lightning strikes is key.
2. A. Restrictive
This information is key because the lightning is so powerful it can even ignite areas that are damp due to rainfall.
3. B. Nonrestrictive
The information that lightning occurs all over the world has no bearing on whether or not is is an amazing phenomenon. This is extra information which can be left out.
4. B. Nonrestrictive
The volume of the thunder is not imperative information to whether or not it follows after lightning. The level of noise is extra information.
5. A. Restrictive
The information about the lightning actually making contact with a person is key for the rest of the sentence. The lightning just occurring may not result in serious injury or death. However, a person actually being struck will usually end up in injury or death.
