The location of the current Sahara Desert and Sahel hosted a giant lake called mega Lake Chad. When did very large lake exist and what does that existence tell you of climate at the time.单项选择题

There were a number of highstands for mega Lake Chad, and these were all after the last ice age during the period called the Holocene. This tells you that what is now desert was once much wetter and only a few thousand years ago.

Mega-Lake Chad reached its biggest extent about 2000 years ago during the time of the Roman Empire. The entire region of the Sahara Desert was much wetter then, allowing the growth of crops to feed all those Roman Soldiers.

There were a number of highstands for mega Lake Chad, and these were all during the last ice age. This tells you that the biggest desert in today’s climate was much wetter during glacial periods.

Mega-Lake Chad reached its biggest extent about 4000 years ago during the expansion of Ancient Egypt. The entire region of the Sahara Desert was much wetter then, allowing the growth of crops to help that ancient civilization grow.