Large deposits of the rare mineral nahcolite formed in salty lakes 50 million to 52 million years ago during the Eocene epoch. Laboratory tests found that, in salty water, nahcolite can form only when the atmosphere contains at least 1, 125 parts per million of carbon dioxide. The statements above, if true, most strongly support which one of the following? ['For most of the time since the Eocene epoch, the level of carbon dioxide in the atmosphere has been lower than it was during most of the Eocene epoch.', 'The atmosphere contained at least 1, 125 parts per million of carbon dioxide during at least some part of the Eocene epoch.', 'No significant deposits of nahcolite have formed at any time since the Eocene epoch.', 'Levels of carbon dioxide in the atmosphere fluctuated greatly during the Eocene epoch.']