The correct answer is: A. A is reliable, B is unreliable, C is reliable.
- A states that the pioneers found an unpleasant and unfriendly environment, which is a reasonable assessment based on the hardships of pioneering work.
- B generalizes that none of the pioneers liked summer because it was dreadfully hot, which seems subjective and might not reflect everyone's experiences, making it unreliable.
- C provides a factual statement about the pioneers building underground homes to adapt to their environment, which is plausible and therefore reliable.