The statement suggests that the cost of living index (COL) will increase due to a recent increase in the price of fruits and vegetables. Let's analyze the options provided:

A. The cost of fruits and vegetables has risen sharply.
This can be inferred from the statement. If the economist mentioned an increase in the price of fruits and vegetables, it suggests that their cost has risen.

B. Consumers have decreased their consumption of fruits and vegetables.
This cannot be directly inferred from the statement. The statement does not provide any information about consumer behavior or changes in consumption patterns. It only mentions the increase in the price of fruits and vegetables.

C. The cost of fruits and vegetables is a major item in the COL.
This can be inferred from the statement. If the economist suggests that the COL will go up due to the increase in the price of fruits and vegetables, it implies that fruits and vegetables are a significant component of the COL.

D. Other items that make up the COL have not significantly decreased in price.
This cannot be inferred from the statement. The statement focuses on the increase in the price of fruits and vegetables and does not provide any information about the price changes of other items included in the COL.

E. Food cost changes are reflected quickly in the COL.
This can be inferred from the statement. The economist suggests that the increase in the price of fruits and vegetables will lead to an increase in the COL next month, implying that changes in food costs are quickly reflected in the COL.

Therefore, the option that cannot be inferred from the statement is option B: Consumers have decreased their consumption of fruits and vegetables.