Final answer:
The presence of fossilized tropical plant remains would most directly support Cardenas and Lamb's conclusion of a wet and warm scenario, as such plants thrive in those particular conditions.
Step-by-step explanation:
If Cardenas and Lamb concluded that the wet and warm scenario is likely correct for the conditions of a basin, the presence of fossilized tropical plant remains would most directly support their conclusion. Fossilized remains of tropical plants indicate that the climate in the past was suitable for such vegetation to thrive, which is consistent with a wet and warm environment.
This is more directly supportive of their conclusion than glacial deposits (which suggest cold conditions), an abundance of desert flora (which suggests arid conditions), or the high elevation of surrounding mountains (which could influence climate but does not directly indicate it was wet and warm).