Final answer:
The recent pine beetle infestations are expected to cause the price of lumber to rise in the next six months, resulting in a decrease in supply of lumber at present.
Step-by-step explanation:
The recent pine beetle infestations in the western provinces of North America and Europe have led to significant destruction of trees. As a result, the price of lumber is expected to rise in the next six months due to a decrease in supply. When trees are infested and killed by pine beetles, there is a reduced availability of lumber. This decrease in supply will subsequently lead to a higher price of lumber in the market. Therefore, the correct answer to the question is:
b. fall now.