The blood coagulation cascade is triggered when (drop down 1) is converted to (drop down 2).

Drop down 1 choices: Prothrombin Factor X Factor IX Factor XI. Drop down 2 choices: thrombin Factor Xa Factor IXa Factor XIa.

I chose drop-down choices Factor X and Factor Xa, because my textbook showed figure 6.23 The coagulation cascade, which stated, "The triggering step is marked with an asterisk." The asterisk is displayed on the downward arrow from X to Xa. Is this the correct answer?

I cannot upload image as .pdf.