Meters Micrometers centimeters millimeters
Answer:
Peer Review
Explanation:
When scientist check other scientists the process is dubbed "peer review".

Since the diameter of helium atom is approximately
, therefore the diameter of helium atom in nano meter,

Answer:
period
Explanation:
A wave takes 0.5 seconds to complete one cycle. It is called the time period of the wave. It is the time taken by the wave to complete one cycle.
The relation between the time period and the frequency is given by :
T = 1/f
Where
f is frequency of the wave
Hence, the correct option is (a) "period".