Explanation

• Humidity in the air was measured by a Hygrometer.
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• A hygrometer is an instrument used to measure relative humidity.
• Humidity is the measure of the amount of moisture in the air.
• A psychrometer is an example of a hygrometer.
• hygrometer.
  
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• The humidity in the air tells us about the ratio of Water vapors in the air

Explanation

in the early 1950s, the first successful vaccine was created by US physician Jonas Salk.

Salk tested his experimental killed-virus vaccine on himself and his family in 1953

First used Salk vaccine in 1955 ( in activated)

while 

A live attenuated (weakened) oral polio vaccine developed by Dr. Albert Sabin and first used in 1961.

Israel launched a polio vaccine drive after 1988 in April 2022

Explanation

Hydrogen (H2) is not a greenhouse gas.

Greenhouse gases are gases in the Earth's atmosphere that absorb and emit radiation, trapping heat and contributing to the Greenhouse Effect.

The main greenhouse gases are:

• Carbon dioxide (CO2)
• Methane (CH4)
• Nitrous oxide (N2O)
• Water vapor (H2O)
• Ozone (O3)
• Chlorofluorocarbons (CFCs)
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)

Explanation

• Most of the weather phenomena take place in the Troposphere layers of the atmosphere
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• Almost all the water vapor in the atmosphere is contained in the troposphere.
• All weather-related phenomena such as the formation of clouds, rain, fog, winds, and storm take place in the troposphere.
  
  

Explanation

Lithium is the lightest metal.

It has the lowest density of all metals.

This making it the least dense metal element.