To assess the reliability of the sentences, we need to consider their content and how they could be verified or supported by historical evidence or sources.
A. The first pioneers to explore the opal fields found an unpleasant and unfriendly environment. - This is somewhat vague and lacks specific evidence or context. It could be considered unreliable unless supported by historical accounts.
B. None of the pioneers liked summer because it was dreadfully hot. - This is a strong statement that makes a blanket claim about all pioneers. It's likely to be unreliable since such a wide assessment of people's opinions is difficult to substantiate.
C. To adapt to the challenging environment, pioneers built underground homes. - This statement is specific and factual, as constructing underground shelters or homes can be a reasonable adaptation to extreme temperatures in certain environments.
Based on this assessment, the most appropriate response is:
A is unreliable, B is unreliable, C is reliable.