Motipur, Bajari, Bhagalpur, and Dalmianagar are not silk textile producing centers in Bihar. The correct answer is Bhagalpur.

Bihar is known for its rich tradition of silk weaving, and Bhagalpur is one of the major silk textile producing centers in the state. It is renowned for its exquisite silk fabrics, especially Tussar silk, also known as Bhagalpuri silk.

1. Bhagalpur - The Silk City:
- Bhagalpur, also known as the "Silk City," is located in the eastern part of Bihar.
- It has a long history of silk weaving, dating back to ancient times.
- The city is famous for its unique handloom silk fabrics, which are known for their exceptional quality and designs.
- Bhagalpuri silk is highly sought after in both domestic and international markets.

2. Tussar Silk:
- Tussar silk is the most prominent type of silk produced in Bhagalpur.
- It is known for its natural golden hue and textured finish, making it a popular choice for sarees, dress materials, and other silk products.
- Tussar silk is made from the silk produced by the larvae of several species of silk moths, primarily the Antheraea mylitta moth.

3. Silk Weaving Process:
- The silk weaving process in Bhagalpur involves several stages, starting from the cultivation of silk cocoons to the final weaving of silk fabric.
- The silk cocoons are harvested and boiled to extract the silk thread.
- The extracted silk thread is then spun into yarn and dyed using natural dyes.
- Skilled weavers use handlooms to weave the silk yarn into beautiful fabrics, incorporating intricate designs and patterns.

4. Products and Market:
- Bhagalpur silk products are known for their elegance and durability.
- The city produces a wide range of silk textiles, including sarees, dress materials, stoles, scarves, and home furnishings.
- Bhagalpuri silk sarees, in particular, are highly esteemed for their fine craftsmanship and unique designs.
- The silk products from Bhagalpur are marketed both locally and globally, attracting customers from various parts of India and abroad.

Conclusion:
Bhagalpur is a prominent silk textile producing center in Bihar, known for its exquisite Tussar silk fabrics. The city's rich tradition of silk weaving, skilled craftsmanship, and unique designs have earned it the reputation of being the "Silk City" of Bihar. Its silk products, especially Bhagalpuri silk sarees, are highly valued in the market for their quality and beauty.