Answer:
The answer is indeed:
undressing uncomfortably
being unable to take his eyes away
being nervous
Step-by-step explanation:
The suspenseful tone of this passage relies on the uneasy mood created by the author. The mood provokes an emotional response in readers and, in this case, it is set by the actions described. Even though the speaker wishes to not look at the picture, he is unable to do so. Readers can imagine him glancing at it as we glance at something we are afraid of; undressing uncomfortably as we do when we feel that someone is watching us; being nervous as if something is about to happen. All those actions contribute to a sense of suspense and uneasiness.