The invention of maize (a type of corn) plastics, which are more environmentally friendly than their petroleum counterparts, can be seen as a reaction to a trend in which sector of the marketing environment?

5) Natural

Explanation:

The two main natural environment trends in marketing are:

natural resources used as inputs that substitute other traditional raw materials (e. g. corn replacing plastic) consumer aversion to increased pollution or an increase in environmental negative effects (e. g. cutting down rainforests)