The correct answer is - ice cores and rock records.
The scientists, mainly the geologists, are studying the climate history and patterns of our planet by mostly using the ice cores and especially the rock records. They also use other things, like the fossils and soils as for additional information. The rock records are very important because they contain lots of materials that can give a relatively accurate information about the climate in certain period, because they can have ash particles, pollen, fossils, and also the way they are can suggest what climate factors influenced their structure. The ice cores are also a good indicator for climate changes, and they provide answers through the different layers of ice that form into specific climate conditions.