$11)$ The Delphi method of forecasting is useful when:

A$)$ a systematic approach to creating and testing hypotheses is needed and the data are usually gathered by sending a questionnaire to consumers

B$)$ when there is little existing data with which to make informed decisions.

C$)$ historical data are available and the relationship between the factor to be forecast and other external or internal factors can be identified

D$)$ historical data is available and the best basis for making projections is to use past demand patterns

E$)$ historical data is used for Analytics and Forecasting.