If the ice of Greenland and Antarctica were to melt, the sea level would rise at least 100 feet or more.
A) If the ice of Greenland and Antarctica were to melt, the sea level would rise at least 100 feet or more.
B) Were the ice of Greenland and Antarctica to melt, the sea level would rise at least 100 feet.
C) Was the ice of Greenland and Antarctica to melt, the sea level would rise at least 100 feet or more.
D) If the ice of Greenland and Antarctica was melting, the sea level would rise at least 100 feet.
E) Should the ice of Greenland and Antarctica melt, the sea level would rise at least 100 feet or more.
Can't be A,C,or E because of at least -> or more
Can't be B because Were is something that occurs in the past and "to melt" is something that occurs in the present
It has to be D