Global warming, *which* is one of the most serious problems, refers to an increase in temperature. Maria Curie, *who* discovered polonium and radium, was born in Warsaw. Hydrogen, *whose* atomic number is 1, is more and more used for vehicles. (+) Alber Einstein, *who* invented the theory of relativity, emigrated to the USA in 1940. Because of the hurricane she lost her house, *which* she had just renovated. Demetri Mendeleev, *whose* parents had 17 children, published the first periodic table. Crude oil, *whose* price constantly goes up, is going to run out. (+) (+) Personally I think these sound a bit funny, although they are correct. I would say "Hydrogen, which has an atomic number of 1,.." and "Crude oil, which constantly increases in price, ...". More discussion here: www.quickanddirtytips.com/education/grammar/whose-for-inanimate-objects