Human activities can alter an ecosystem and bring about the extinction of a species. such activities include any of these except a) hunting a species to extinction. b) assuring a habitat remains unharmed. c) introducing toxic compounds into food webs. d) introducing a new species into an environment.

The correct answer is option B, assuring a habitat remains unharmed

Explanation:

Among all the given options , human activities preserving the ecosystem is depicted in option B where human is not trying to disturb the ecosystem. While in all other options, hunting a species upto extinction will create disappearance of an species from ecosystem, introducing toxic compound to a food web will lead to transfer of toxic compound to each trophic level  and in the last option D,  even if a new species is introduced in the food web, it will destablize the food web thereby making the ecosystem as unstable.

hey, i believe your answer would be d. sugar ribose and the base uracil. i believe this is the answer, because rna consists of sugar ribose, adenine, guanine, cytosine, and uracil.

your first option is incorrect, because that's dna. where it consists of sugar deoxyribose, adenine, guanine, cytosine and thymine.

your second option is also incorrect, this is because sugar deoxyribose is in dna, and uracil is in rna. these two do not make sense together.

your third option being incorrect, because sugar ribose is in rna, but not the base of thymine. rna consists of uracil, not thymine.

lastly your fourth option being correct! this answer is correct, because both sugar ribose, and the base uracil are in rna! ~

answer is d. sugar ribose and the base uracil.