How do weather observations become climate data

Explanation:

Observations of Weather are the Foundation of Climate Products 

Cooperative Observers Program (COOP) Stations in the lower 48 states. Image source: COOP 

Around the globe, millions of weather observations are recorded each day, by both human observers and automated instruments. In the United States, daily observations at stations that meet specified criteria, methodically collected by volunteer observers and automated weather stations, are used to document our weather and climate. One volunteer weather observer program in the United States is the Cooperative Observer Program (COOP). This program, which includes more than 11,000 stations, is key to obtaining accurate observations across the country. Started in 1890, the COOP network now spans all corners of our nation: from mountaintops to meadows, urban to rural regions, and from seashores to suburbs.

the answers are a and c