TOEFL Listening: TPO-TOEFL阅读TPO - QAED45QA00IPP4AON$

All of the following questions about geological features on Mars are answered in paragraph 3 EXCEPT: A. What are some regions of Mars that may have once been covered with an ocean? B. Where do mission scientists believe that the river forming the delta emptied? C. Approximately how many craters on Mars do mission scientists believe may once have been lakes filled with water? D. During what period of Mars' history do some scientists think it may have had large bodies of water?