The correct option is B A. all
B. lymphocytes
C. immune
ADA gene codes for the production of Adenosine Deaminase enzyme. Adenosine deaminase eliminates a molecule called deoxyadenosine, which is toxic to lymphocytes. This enzyme is produced in all cells, but the highest levels of adenosine deaminase occur in immune system cells called lymphocytes. Thus for a healthy immune system, functional ADA is essential and if it is deficient the individual suffers from a disorder known as Severe Combined Immunodeficiency (SCID). People with SCID are prone to repeated and persistent infections that can be very serious or life-threatening.