Photographs from the satellites launched by NASA at the early 1970s have proved invaluable to the mapping of remote areas.

Photographs from the satellites launched by NASA at the early 1970s ha

1.	Photographs from the satellites launched by NASA at the early 1970s have proved invaluable to the mapping of remote areas.
A.	owards
B.	rom
C.	ince
D.	o improvement
Answer» D. o improvement