Briefly describe the history of the metric system as it applies to the meter and how the definition of a meter has changed over time.

Answer and explanation;

In 1670 Gabriel Mouton, Vicar of St. Paul’s Church and an astronomer proposed the swing  length  of  a  pendulum  with  a  frequency  of  one  beat  per  second  as  the  unit  of length.

In 1791 the Commission of the French Academy of Sciences proposed the name meter to the unit of length. It would equal one tens-millionth of the distance from the North Pole to the equator along the meridian through Paris.It is realistically represented by the distance between two marks on an iron bar kept in Paris.

In 1889 the 1st General Conference on Weights and Measures define the meter as the distance between two lines on a standard bar that made of an alloy of 90%platinum with 10%iridium.

In 1960 the meter was redefined as 1650763.73 wavelengths of orange-red light, in a vacuum, produced by burning the element krypton (Kr-86).

In 1984 the Geneva Conference on Weights and Measures has  defined  the  meter  as  the  distance  light  travels,  in  a  vacuum,  in 1299792458⁄ seconds  with  time  measured  by  a  cesium-133  atomic  clock  which  emits  pulses  of radiation at very rapid, regular intervals.

which three statements are true about all alloys?