题目选项分析

In the last few years, plant scientists have been able to genetically engineer seeds to produce crops highly resistant to insect damage. Farmers growing crops with these seeds will be able to spend significantly less on pesticides. This cost reduction would more than make up for the higher cost of the genetically engineered seeds. Clearly, therefore, farmers who grow crops from genetically engineered seeds will be able to reduce their costs by using them. Which of the following, if true, most weakens the argument?

【选项】Plant scientists have not yet developed insect-resistant strains of every crop that is currently grown commercially.