The correct answer is option 'D' - All of these.

Emotions on realizing:
When the author realizes that he has reached both the summits, he experiences a range of emotions. These emotions can be categorized into humility, sorrow, and confidence.

Humility and sorrow:
Reaching the summits of two mountains is a remarkable achievement, but instead of feeling pride or arrogance, the author feels humility. This indicates that the author recognizes the magnitude of the accomplishment and acknowledges the power and beauty of nature. The author may also feel a sense of sorrow because reaching the summits might have come at a cost, such as physical exhaustion, mental strain, or even the loss of fellow climbers. This sorrow can also arise from the realization that the journey is over and there may not be another opportunity to experience such a feat.

Confidence:
On the other hand, the author also experiences confidence. Reaching the summits of two mountains requires determination, perseverance, and skill. The successful completion of this challenging task can boost the author's confidence and self-belief. It serves as a validation of the author's abilities and can inspire a sense of accomplishment and satisfaction.

Overall, the author's emotions on realizing both the summits are a mix of humility, sorrow, and confidence. These emotions reflect the author's deep appreciation for the accomplishment, the recognition of any sacrifices made, and the confidence gained from overcoming challenges.