While anti-PSA is coated on to the well in total PSA estimation, the antibodies coated in free PSA is.. The same antibodies that is coated for total PSA

While anti-PSA is coated on to the well in total PSA estimation, the antibodies coated in free PSA is?
a. The same antibodies that is coated for total PSA
b. Same antibodies in large amount
c. Same antibodies in very low amount
d. Different antibodies.

(a) different antibodies.