The correct option is A they were greatly relieved
This question requires you to make an inference, i.e., to choose an answer that is not directly stated in the passage but is implied.
If the narrator and his friend thought the light came from far away, they could have been surprised that the light was close by. However, they sometimes thought the light was near and sometimes thought the light was far. Therefore, it is unlikely that they were surprised. Option A is therefore incorrect.
There is nothing to suggest disappointment in the passage. Option D is incorrect.
They may have been pleased, so option C may be a possibility for a correct option.
However, the more precise answer is option B, that the narrator and his friend were relieved. We infer this from the fact that they were uncomfortably stumbling along in the darkness and that they would reach their destination when they arrived at the source of the light.