【单选题】Eight times within the past million years, something in the Earth's climatic equation has changed, allowing snow in the mountains and the northern latitudes to accumulate from one season to the next i...
A.
Marine sediments have allowed scientists to amass evidence tending to confirm that astronomical cycles drive the Earth's glacial cycles.
B.
The ratio between two different isotopes of oxygen in seawater correlates closely with the size of the Earth's ice sheets.
C.
Surprisingly, single-cell marine organisms provide a record of the Earth's ice ages.
D.
The Earth's astronomical cycles have recently been revealed to have an unexpectedly large impact on the Earth's climate.
【简答题】Instead of “ melting pot ” , America is now regarded as a ______, which means immigrants mix harmoniously and keep their distinctive culture and customs at the same time.
【单选题】The United States today is no longer considered a“melting pot”society by many of its residents._________ ,many people prefer the term“salad bowl”.