Step 1: Analyze the word relationship. The initial pair, "Sitar : Guitar," comprises stringed musical instruments. The objective is to identify a word related to "Tanpura" analogously.
- "Tanpura" is a stringed instrument, necessitating a stringed instrument as the missing word.
- The available choices are:
\(\hspace{1cm}\)- Trumpet (wind instrument)
\(\hspace{1cm}\)- Violin (stringed instrument)
\(\hspace{1cm}\)- Harmonium (keyboard instrument)
\(\hspace{1cm}\)- Mridanga (drum)
Step 2: Determine the correct answer. In the category of stringed instruments, "Violin" exhibits the closest similarity to "Tanpura." Therefore, the correct option is 2. Violin.