Too strong. The author never indicates “certainty” that heirloom crops will produce the same yields as commercial counterparts. In fact, the author suggests that heirloom crops might produce lower yields, but they’re still valuable due to genetic diversity.

Not supported, because heirloom crops are not currently used to maintain the genetic base of North America’s crops. Researchers are examining ways to integrate indigenous knowledge regarding heirloom crops, but this doesn’t imply that heirloom crops are currently part of the genetic base of North American food crops.

This best captures the author’s belief that end of the passageheirloom crops are valuable for preserving the genetic diversity of crops. It wouldn’t make sense for the author to propose attention to heirloom crops as a “possible solution” to the eroding genetic base of crops if the author didn’t believe that heirloom crops would help diversify the genetic base.

Not supported, because researchers have only recently turned their attention to indigenous techniques for maintaining heirloom crops.

Not supported, because the author indicates that the market economy is something that discourages heirloom crops.