The Formation of a Blood Clot Involves the Following Events

The formation of a blood clot involves the following events.What is the correct sequence?
1) the conversion of fibrinogen to fibrin
2) the formation of prothrombin activator
3) the conversion of prothrombin to thrombin

A) 1, 2, 3
B) 2, 3, 1
C) 3, 2, 1
D) 2, 1, 3
E) 3, 1, 2