As the percent of iron in an igneous rock increases its density

As the percent of iron in an igneous rock increases, its density will increase. Igneous rocks are rocks with a formed by the solidification of molten lava or magma. Magma is molten rock which is formed inside the earth's core. There is a difference between igneous rocks that have formed under the earth's crust or as a result of volcanic activity. Igneous rocks that contain a high percentage of iron and magnesium are dark in colour. An example of an igneous rock is Basalt. 

B. thrombin causes sticky fibrin filaments to form the clot.
from the options this is the best answer however before this can happen prothrombin needs to convert into activated thrombin through the complement system.