Plzz answer

which of the following is true of bacteria?
a bacteria are always indicative of disease.
b bacteria are single-celled microorganisms.
c bacteria can be seen with the naked eye.
d bacteria are not found on the skin.

Select the situation bellow that would produce a total displacement of zero. a. a trip to the moon and then to mars b. a horse galloping from one end of a field to another c. the criss-crossing path of a bug as it flies from flower to flower d. a round-trip ride to school and back

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

When a gasoline engine burns gasoline, what type of chemical reaction is occurring?