What is the adjective phrase in the sentence. if a sentence has no adjective phrase, choose none. in the greenhouse, gardeners are testing a new kind of fertilizer on plants. a. are testing. b. none. c. in the greenhouse. d. of fertilizer

i believe it is the first choice (1.)

because the major theme is(“both the wild and civilization have rules.”)

and also as u said,( based on what buck learns within the call of the wild, "both the wild and civilization have rules".this is true of humans within society as well.