Final answer:
The best sentence to continue the focus of the paragraph about the office party is the one expressing the writer's discomfort in conversing with Smith and contemplating expressing their feelings.
Step-by-step explanation:
To continue the focus of the paragraph about the office party and the interaction with Smith, the sentence that could be added is "Having a conversation with Smith was uncomfortable and I considered expressing this to him." This option aligns with the existing tone and context, which describes discomfort and a problematic situation with Smith at the office party. It also reflects the writer's internal conflict and adds more depth to the narrative, highlighting the challenges of office social dynamics.