Step 1: Understanding the Base.
In this question, we are asked to identify the base used in the given reaction. The base is crucial in nucleophilic substitution or elimination reactions.
Step 2: Analyzing the Options.
- (A) \( \text{(CH}_3\text{)}_3\text{N} \) is not the correct base for this reaction.
- (B) \( \text{CH}_3\text{NH}_2 \) is a primary amine, but it is not the desired base here.
- (C) \( \text{CH}_2\text{NH}_2 \) is also not the correct base for this reaction.
- (D) \( \text{(CH}_3\text{)}_2\text{NH} \) is the correct base, as it is a secondary amine, making it effective in promoting the desired reaction.
Step 3: Conclusion.
The correct answer is (D) \( \text{(CH}_3\text{)_2\text{NH} \)} as it is the correct base for this reaction.