The learners said,''We have been studying a lot this week.'' change to indirect speech​

In this excerpt from "colonialism in the united states" by henry c. lodge, which word is closest in meaning to the word indelibly? long after the world to which it belonged has vanished, a habit of thought will live on, indelibly imprinted upon a race or nation, like the footprint of some extinct beast or bird upon a piece of stone.