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a lichen is a symbiotic association between a fungus and green algae. the green algae carry out photosynthesis and provide the fungus with sugars. what does the fungus provide the green algae in return?

a. an energy source
b. sugars from photosynthesis
c. water and minerals
d. nutrients and oxygen

Waste water from industries and domestic sources can be treated by chlorination or ultraviolet radiation. there are pros and cons to using either chlorine or uv radiation to kill harmful microorganisms. what is one reason chlorination would be preferred over ultraviolet radiation? a) chlorine only eliminates visible impurities and is ineffective against microorganisms. b) chlorine not only kills bacteria but provides a residual effect on returning microorganisms. c) uv radiation can be used only to treat drinking water and is ineffective in treating waste water. d) ultraviolet radiation is more effective