Final answer:
The correct conjunction to complete the given sentence, highlighting the father's agitated reaction to not going outside, is 'indeed' as it emphasizes the link between his agitation and subsequent actions. The correct answer is option d.
Step-by-step explanation:
The correct option to complete the sentence "Not being able to go outside on such a nice day, father became very agitated; _____, he began to jump up and down and wave his arms wildly." is d) Indeed.
This conjunction fits the context as it serves to provide emphasis or confirmation of the father's agitated state leading to the described action. It implies that the action that follows (jumping up and down, waving his arms) is indeed a result of the agitation mentioned earlier.
The other options, a) Similarly, b) Nonetheless, and c) On the other hand, do not properly connect the two parts of the sentence because they either imply similarity to another action, contrast, or continuation despite something else, respectively, which does not fit the context provided.
Option d) Indeed is the correct option for the final answer.