Could be false. There could be other factors that influence a false chicory plant’s height besides rainfall. The stimulus does not tell us that rainfall is the only factor that would cause one plant to be taller or shorter than others.

Could be false. Although we know that a plant with a longer-than-average taproot would have an above-average height, this doesn't imply that the plant probably received more than twice the average rainfall. The stimulus does not tell us that rainfall is the only factor that would cause one plant to be taller or shorter than others. So the plant could be taller than average for reasons other than rainfall.

Could be false. The stimulus does not tell us that it is necessary for a plant to receive more than average rainfall in order to be above-average height. We know that the more rain, the taller the plant tends to be, but it's still possible for a plant to be above-average height while only getting average or below-average rain.

Could be false. There could be other factors that influence a false chicory plant’s height besides rainfall. The stimulus does not tell us that rainfall is the only factor that would cause one plant to be taller or shorter than others.

Must be true. A plant’s height is always twice as long as the plant’s taproot, and plants receiving more than twice the average rainfall are always above-average in height. Therefore, a plant receiving more than twice the average rainfall will have a longer than average taproot.