Why do doctors check for swollen lymph nodes?
A. Lymph nodes are the site of white blood cell production.
B. Memory cells are stored in the lymph nodes.

c. It is impossible to immunize the lymph nodes.
D. Bacteria and viruses mostly attack the lymph nodes.

Astudent poured a solution of bromothymol blue indicator into three test tubes. then he placed an aquatic plant in two of the test tubes, as shown below. he placed a stopper on each test tube and placed them all in the dark for 24 hours. bromothymol blue turns from blue to yellow in the presence of co2