Aquestion that arises based on the information in "plastics, human health, and environmental impacts: the road ahead" is "how safe are plastics for humans and the environment? "
the author effectively answers this question by _[blank]_.
which option best completes the sentence?
plastics, human health, and environmental impacts: the road ahead

"The author effectively answers this question by _plastics_.". See explanation below.

Explanation:

For this case we are interested in answer the following two questions:

"Plastics, Human Health, and Environmental Impacts: The Road Ahead" is "How safe are plastics for humans and the environment?"

And as we can see the questions are related to "Plastics". And that should be the correct option on this case . Because impacts on Human health is not the factor is a consequence of the use of Plastics and the other option environmental impacts again is an effect consquecne of the Plastics on the environement.

So then "The author effectively answers this question by _plastics_."

He can analyze how the different types of plastics can affect the environment, animals and the human life. He can take in count that plastics is is not a digerible food for any animal and human and takes too much time to degradate.