How do weather observations become climate data?
A. the temperatures that happen during one season are recorded daily
B. air pressure, temperature, humidity, wind speed and direction are recorded for a
specific area
C. weather conditions are measured at thousands of locations every day for 30 or
more years
D. weather is recorded over a few weeks in one area. ik b is wrong

Weather observations become climate data when weather conditions are measured at thousands of locations every day for 30 or  more years.

Explanation:

According to the definition of climate, observations of the weather conditions are required for a very long period of time, even 30 years or more, registered in many places.

Weather refers to the presence of certain characteristics such as air pressure, temperature, humidity or wind speed in a given place in short periods, such as 24 hours.

Meteorologists refer to the climate taking into account the information collected from characteristics, such as temperature, air pressure or rain, in many places and for long periods of time, establishing an average value and with the possibility that this helps to predict weather behavior.

All weather information collected around the world over a period of 30 years or more becomes average values of temperature, air pressure, humidity, speed and wind direction that serve as climate data to predict the behavior of the weather in a determined place.

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Meteorology and wheater link

"a.) well–developed vascular system."