i'm creating word templates at my workplace.

i'm looking for a way to make sentences appear and disappear based on the
selections of the person who is filling the word template.

for example, there's a sentence which requires an answer "yes" or "no" from
a drop down menu. if the user answers yes an another sentence will be shown
on the next line. if he answers no the sentence wll not be shown and neither
will be the line it would be if he chose yes.

what would be the best way to do that kind of trick?