Um.. what item? and you just posted the answer?
Answer: Memory B cells
Explanation:
Memory B cells remember the same pathogen for faster antibody production in future infections.
If you talk about the process of fission in the nuclear field then the most used is U-235 because is the easiest to use. Have in mind that the majority of uses of uranium is U-238 but the easiest to be used is U-235
Answer:
The element carbon is actually the chemical basis for all life. It is the most important because it can be used to form many essential compounds.
Carbon takes up almost 20% of the weight of an organism, and it is essential for them to live and grow. (Also to reproduce.)
