I read some books in cfa program. what is risk of a stock in the Markowiz line? I do not know.

I think that the risk of a stock contain the following risk
1. risk from business. this risk is from business competition, business cycle or changes in customers demand among the other.
2. risk not from business . this is from fire, war, or earthquake.
3. risk from the craziness of the market.

we can reduce the risk 1. doing so mean doing business
we can not reduce the risk 2.
we can not reduce the risk 3. but risk 3 can offer a chances to buy stock of low price.
now we talk about effect of diversification on 3 the risks. I want to research more on effect of diversification on each of risk. I think cfa makers can do this job. the purpose is to reduce each risk by diversification.

I am an individual stock investor who has got some success over a few years.