In the seventeenth century, North America was vast and unconquered, ____ only at great cost. A. by promising riches but by yielding its bounty B. its riches were promised but its bounty yielded C. it promised riches but yielded its bounty D. promising riches but yielding its bounty Note: I have no idea what the sentence is talking about (especially what comes after “but”)… what do you think is the meaning of the sentence? Also, shouldn’t it be “at A great cost?”