Help!
1) What does the word invasive mean?
2) What does it mean to be an invasive species?

An invasive species is an organism that is not indigenous, or native, to a particular area.

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Explanation:

#1 especially of plants or a disease) tending to spread prolifically and undesirably or harmfully

#2 An invasive species is an introduced organism that becomes overpopulated and negatively alters its new environment.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

i think the answer is b.