Which of the Following Is a Consequence of Changing Climate

Which of the following is a consequence of changing climate conditions in the late eleventh and early twelfth centuries?

A) Drought forced the Seljuk Turks to migrate out of the steppes and invade Baghdad.
B) Abundant rains increased crop yield in Egypt.
C) Global warming permitted the spread of crops such as citrus and sugar,which had originated in China.
D) Severe weather closed the main trade routes through Central Asia.