Title: Renewable energy commercialization.
Question: Photovoltaic and solar-thermal plants may meet most of the world's demand for electricity by what year?

Title: Valencia.
Question: Who said the Valencia derailment was fortuitous?

Title: Royal Institute of British Architects.
Question: What was the first year in which RIBA's Royal Gold Medal was given?

Title: Ottoman Empire.
Question:
Who was Mehmed's successor?