Which of the following correctly describes a positive way in which hydrogen fuel cell technology can affect environmental quality or way of life? It is easy to store safely and distribute globally.
It allows for the same efficiency as gasoline-run engines.
It can be used to power small and large electrical systems.
It can only be used without combining with other energy resources.

The vaccine in a flu shot contains weakened flu viruses. how does a flu shot work with the immune system? a. it destroys lymphocytes. b. it destroys macrophages. c. it activates macrophages. d. it activates lymphocytes.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

An area has a few days of low humidity, warm air temperature, and high air pressure. what kind of weather is this area experiencing? o fog o snow storms o sun