Sometimes enlarged lymph nodes may be the result of non-Hodgkin's lymphoma but more often are the ...

Sometimes enlarged lymph nodes may be the result of non-Hodgkin's lymphoma but more often are the result of infection. Which of the following is the primary way to rule out that infection?
 
  a. A biopsy is done immediately and is looked at microscopically.
  b. Antibiotics are given to see whether the lymph node has decreased in size.
  c. Measure the size to determine whether the lymph node is larger than a certain size; if so, it is a tumor.
  d. Measure the patient's temperature; if it is elevated, the swelling is due to an infection.