Which of the following best describes immunoassay technique?
(a) It is not sensitive below concentration of 10 mg/mL
(b) It can be used for therapeutic drug monitoring in plasma or serum
(c) It relies on inelastic scattering of monochromatic light in the near infrared range
(d) It is a highly sensitive technique that is based on ionisation of chemical species and sorting out the ions based on their mass to charge ratio