Algae are utilized by humans for a variety of beneficial purposes. why are photosynthetic algae considered one of the most important groups of organisms on our planet?
a. they are poor sources of vitamin
c. b. they produce chemicals that can treat health problems.
c. they produce much of the earth’s oxygen.
d. they produce chemicals that can make plastics, waxes, and paints.

Which of the following describe possible scenarios? a) an object has zero instantaneous velocity and non-zero acceleration. b) an object has negative acceleration and is speeding up. c) an object has positive acceleration and constant velocity. d) an object has positive velocity and zero acceleration. e) an object has increasing positive position and negative velocity. f) an object has decreasing positive position and negative acceleration.