Final answer:
The correct term for a source of historical climate data is 'Proxy,' option (c) which includes natural records like fossils, ice cores, tree rings, and sediment cores, providing indirect evidence of past climates.
Step-by-step explanation:
The correct term for a source of historical climate data is C. Proxy. Proxies are secondary sources of information used by scientists to interpret past climates because direct measurements of climatic variables from the past are not possible. Common examples of proxies include fossils, ice cores, tree rings, and sediment cores.
These natural records contain information that, when analyzed, can provide insights into the Earth's climate history. For instance, the coiling direction of foraminifera shells can indicate relative seawater temperatures at the time those organisms existed.
Similarly, the thickness of annual rings in trees can reveal growth patterns influenced by temperature and precipitation variations over time.