Answer:
The correct answer would be D.Alveolar sacs are surrounded by thin capillaries where gases can be exchanged.
Alveoli are tiny sacs which form the site of gas exchange in the lungs.
The features of alveoli which help in gas exchange are:
- They increase the surface area in the lungs thus, more space is available for gas exchange.
- They have very thin walls, as thin as the thickness of a single cell only.
- They are surrounded by a bunch of thin capillaries which exchange gases with alveoli.
Answer:
There are many many things in the world that produces Carbon. The largest source of greenhouse gas emissions from human activities in the United States is from burning fossil fuels for electricity, heat, and transportation. All of these produce Carbon into the atmosphere and warm the planet
Answer:
B) if two species are closely related.
Explanation:
DNA analysis is used to determine the relationship between two species in order to check their relations with each other because DNA molecules has all the information about the organisms. If there is more similarities between two organisms so they are more closely related to each other while on the other hand, if there is no similarities between two species so we can say that there is no relationship exists between two organisms or species. All this discussion describes the usefulness of DNA analysis.
The process of DNA replication begins with one double-stranded molecule of DNA. The two strands of this molecule separate during replication, and DNA polymerases add complementary nucleotides to each strand. The end results of DNA replication are two identical DNA molecules
