My answer will be that the letter "A" in the chromosome refers to "adenine", which is considered as one of the five nitrogenous bases that are part of the nucleic acids (DNA and RNA), which was named in 1885 by Albrecht Kossel.
The Answer is D
Without a host, a virus is basically inert and useless. They cannot function outside a host organism.
Answer: Secondary Tissues
Explanation: They are the xylem and phloem.
