Conclusion:Experts predict that the use of bamboo in the construction industry will soon see a rapid increase because bamboo is better.
Pattern: The pattern to me seems like "causal Pattern". Since, Bamboo is better and environmental friendly, author predicts the its uses will see rapid increase in construction industry.
Underlying Assumption with this pattern : 1) It is not a coincidence (1) There is no other cause of such belief
How to strengthen ? : If we prove 1) it is not a coincidence (2) Provide an additional example to support the cause. (3) Rule out other possible causes
Answer choices:1) It restrict the availability of Bamboo to specific areas which may not favour the increased usage which author is predicting. - Wrong choice
2) Same reason as A above - Wrong choice
3) Wrong choice as it is providing an alternate to Bamboo which will weaken the author's prediction
4) Supports the argument by giving added advantages of Bamboo - Correct answer
5) Out of scope - No where we are concerned about what environmental organisation are saying. - Wrong choice
Hence, IMHO, D is the correct answer.