The standard unit of time, the second, is now defined with reference to
a. the Earth's revolution period.
b. the mean solar day.
c. the cesium-133 atom.
d. the Earth's rotation period.
Question 2
The standard unit of length, the meter, is now defined with reference to
a. a meridian on the Earth.
b. the French meter.
c. the speed of light.
d. a platinum-iridium bar.
e. a member of the royal family.