They are rich in hydrogen and helium, they have unlimited supply of hydrogen, they have a strong gravitational pull.
Explanation:
Space where huge size of gaseous and dust cloud is present is called nebula. It is mainly made of hydrogen and helium. Nebula exist in the space which is between the stars and it is call as interstellar space.
Helix nebula is closest nebula which is near the earth. It’s distance from earth is about 700 light years.
Dark nebulae are very dense as well as cold. Nebula can be divided into dark nebula and bright nebula. The gas which is present between the stars is always combine with solid grains cosmic dust.
Answer:
Background extinction
Explanation:
The background extinction refers to the diminishing of the species at a fairly slow and constant rate. This extinction takes place because of the various environmental factors namely the changing climatic conditions, spreading of diseases, and destruction of habitat. It plays an important role in the natural process of evolution. This has been taking place continuously throughout the geological time and the species are undergoing continuous evolution over a specific period of time.
B , d and e. I believe that is correct
The graph records every electrical phase of the heartbeat, and each beat is triggered by pacemaker cells. A EKG not only records the electrical phase, but it records the strength and timing of every impulse generated from the upper right chamber of the heart. Each of these recordings can be quickly and easily evaluated to determine whether or not there is an abnormality but this can only be recorded if the abnormality is recorded during the test.
