Which phrase best describes a semidiurnal tide pattern?

a

Explanation:

a is two high tides and two low tides each month

The limitation of using antigen concentration in order to determine the path of infection is that if one has been vaccinated for the infection, then his or her immune system has already produced the antibodies against the antigens. Thus, it can generate an inaccurate result, in the case of ELISA test.  

An ELISA test also known as an enzyme-linked immunosorbent assay refers to a test, which finds and calculates the number of antibodies in the blood. The test is beneficial in finding the antibodies associated with a certain kind of infectious conditions.