It helps compare the frequencies of light.
B) Cell wall.
Hope this helps!
-Payshence xoxo
Answer:
The correct answer is biological.
Explanation:
When any pathogen invades the body, it has to pass several lines of defence. The first barrier is the skin and mucous membrane which is a physical and chemical barrier. The second line of defence is the non-specific response by macrophages, neutrophils and interferon. After crossing these two barriers the third line of defence comes into action in which, the B- cells and T-cells act specifically on the pathogen and destroy it.
I would go with A because its the only one that makes since. The pencil would have to fall eventually, and out of process of elimination I'd go with A .
Hope this helps ...
