Sales of organic produce have grown steadily over the last decade, increasing at a rate far exceeding conventional produce.

✓ Correct Answer: Option D

The original sentence makes an illogical comparison, comparing a 'rate' to 'conventional produce'. To correctly compare rates, a pronoun ('that') must be used to refer back to 'rate,' ensuring a comparison between 'the rate of organic produce' and 'the rate of conventional produce.'