Question

When the readers must figure out the author's meaning on their own, the author has written his or her statement

implicitly
impressively
explicitly
exponentially

Answer 1

Implicitly, because they are doing it in a way that is not directly expressed; tacitly.

Answer 2

The answer: implicitly.

An implicit meaning is, as opposed to an explicit meaning (that is to say, overt meaning), is one that entails a certain effort on the side of the reader which is part of the hermeneutical exercise that any reading involves. This means that the reader must interpret what is written in order to capture the meaning that the author implied in his or her text.