Which of these is not a characteristic of white dwarfs? choose the correct answer.
a long period of existence
a hot, extremely dense core
a ring-like planetary nebula
a position in the lower left of the h-r diagram

Nasa scientists must work together to make sure that everything is correct and accounted for when launching a shuttle. besides a physicist, what other type of scientist would be in making sure that the shuttle has the appropriate type and amount of fuel to reach its destination?

Which sequence correctly shows the path of carbon dioxide during repiration?

Vaccines are weakened forms of disease causing microorganisms, which are given to patients to prevent disease. after the vaccine is administered, the immune system responds by creating a(n) to recognize the a.) antibody, antibiotic b.) antigen, antibody c.)antibiotic, antibody d.)antibody, antigen