Step 1: Split the industry in two:
Cotton textiles have two stages. Spinning turns cotton into yarn. Weaving turns yarn into cloth.
The question says spinning is strong but weaving gives poor quality cloth. So we look for a weakness that belongs only to weaving.
Step 2: Where is weaving weak?:
Spinning is concentrated in big mills, so it can grow strong. Weaving is split among a very large number of small handloom and powerloom units.
Small, scattered units cannot take up the fine yarn made by the mills in a proper way. The yarn quality is not fully used.
Step 3: Test the other options:
Option A is not a fact, since India makes its own yarn in large quantity.
Option C is not a fact, since most weaving is not done in heavily mechanised mills.
Option D does not explain the problem, because the skill of Indian weavers is not the cause of weak fabric quality.
Step 4: Conclusion:
Option B names the real cause, the decentralised weaving structure.
In short, the best yarn from the mills does not reach the small weaving units in a full measure, so the cloth stays of lower quality.
Final Answer:
The most appropriate reason is option B.
\[ \boxed{\text{B. Limited use of high-quality yarn due to decentralised weaving structure}} \]