【单选题】

{{I}}Questions 11—13 are based on the following passage about the effect of crops to the life ofCanadians during the early years of this century. You now have 15 seconds to read Questions 11—13.{{/I}} When did most farmers have to pay their debts

A、When crop failure caused depression.
B．When the autumn harvest had just been completeD、
C．When the wheat prices became increasingly high.
D．As soon as the Winnipeg GrainExchange demanded payment: