For this question you need to draw together information from Figure 1 and Figure 2.
The disappearance of the rhinoceros, hippopotamus and aurochs from Saharan rock art happened

• after the level of Lake Chad had been falling for over a thousand years.
• at the beginning of the most recent Ice Age.
• in the middle of the period when Lake Chad was at its highest level.
• at the beginning of an uninterrupted dry period.