What are the alternative energy sources currently show great promise but need considerable development to be commercially applicable on a large scale?

Which season occurs in the northern hemisphere when the sun is at its lowest point in the sky

The chemical or mechanical process by which rock is gradually broken down eventually becoming soil

All of the following actions are examples of civil disobedience, except a.) refusing to pay an unfair tax b.) refusing to use government services c.) participating in a protest march d.)planning a riot to destroy a government riot