The two types of main ideas are stated and implied ones.
You still alive?
what are the two main types of environment
there are two main types the marine and freshwater
The two main types of economy are Command and Traditional.
The two main types of friction are kinetic and static.
the two main types of communications are emailing and socialising
The two main types of friction are kinetic and static.
what are the two main types of environment
The two main types of rockets are, Solid Fuel and Liquid Fuel
The main types are Serial and Parallel.
Metallic and non-metallic.
Light (electromagnetic radiation) forms a continuous spectrum there are no two main types.
Aerobic fermentation and anaerobic fermentation are two main types.