What does hematocrit measure?
a. the time required for erythrocytes to settle to the bottom of an upright tube at room temperature.
b. the time it takes for blood to clot.
c. how well platelets interact with blood vessel walls to form clots.
d. the percentage of the volume of whole blood that is made up of red blood cells.

The answer is a  Hematocrit measure the time for erytrhocytes to settle to the bottom of the upright tube at room temperature.

Explanation:

Hematocrit is the measurement of  percentage of red blood cells or RBC  in a given blood sample.The normal RBC percentage  in blood  of male is 40 percent to 50 percent and in case of female blood is 36 percent -44 percent .

                  The measurement of RBC of a blood sample is very much important because RBC performs the main function of blood that is to transport oxygen and carbon di oxide to and from the body.

                         Hematocrit is done to test anemia(decreased percentage of RBC) and Polycythemia(increased percentage of red blood cells ).