Which statement gives the current SI definition of the metre?
a) Path travelled by light in air in a time interval of 1/299792458 second.
b) Distance between two fine lines engraved on a platinum–iridium bar at 0∘C kept at Sèvres.
c) Path travelled by light in vacuum in a time interval of 1/299792458 second.
d) 1650763.73 wavelengths of orange–red radiation emitted by krypton-86 in vacuum.