Misc: what is the element for the symbol Se?

Questions

Which english engineer developed the safety lamp for miners at the same time as Humphrey Davy?

Which city in Sudan, the scene of a battle in 1898 was the residence of the mahdi?

In which geographical feature is a caldera found?

Who was a co founder of the German Gree party in 1979 and became one of the best known green mps in the world?

Whose law states that equal volumes of gas contain equal numbers of molecules when at the same temperature and pressure?