How Do Scientists Estimate How Old the Solar System Is

How do scientists estimate how old the solar system is?

A) They make a guess: no one really knows how old the solar system is.
B) They measure the speeds and distances of galaxies, and calculate the time it took for them to travel that distance.
C) They measure the abundances of radioactive elements in meteorites, and use their half- lives to calculate the age.
D) They look up the answer in a book.
E) They measure how fast the Sun is losing energy, and how much energy it has to lose.