Although the pesticide TDX has been widely used by fruit growers since the early 1960' s, a regulation in force since 1960 has prohibited sale of fruit on which any TDX residue can be detected. That regulation is about to be replaced by one that allows sale of fruit on which trace amounts of TDX residue are detected. In fact, however, the change will not allow more TDX on fruit than was allowed in the 1960' s, because __. Which of the following most logically completes the argument? ['pre-1970 techniques for detecting TDX residue could detect it only when it was present on fruit in more than the trace amounts allowed by the new regulations', "at least a small fraction of the fruit sold each year since the early 1960's has had on it greater levels of TDX than the regulation allows", "many more people today than in the 1960's habitually purchase and eat fruit without making an effort to clean residues off the fruit", 'the presence of TDX on fruit in greater than trace amounts has not been shown to cause any harm even to children who eat large amounts of fruit']