(a) The bulk and the heavy weight of a steam engine is not suitable for generation of electricity in a temporary forest camp.
Water needs to be heated to produce steam. This takes time and therefore engine can't start instantly.
(b) Petrol engine is suitable for the location. However, petrol engine is spark ignition engine. Spark plug is a unreliable component of this engine.
(c) Hand operated dynamo is suitable for the location. But is not suitable for generation of electricity for several hours.
(d) Diesel engine is suitable for the location. Its working is not dependent on unreliable spark plug as diesel engine is compression
Temperature of air rises as it is highly compressed in a chamber. Diesel is injected on the heated air in the form of a fine spray. Due to large surface area of the sprayed diesel globules the heated air ignites it.