plot explanation - How did Thresh know that Katniss befriended Rue in Hunger Games?

In The Hunger
Games, Katniss is attacked by Clove, but saved at the last moment when Thresh kills
Clove. Thresh is then in a position to kill Katniss, too, but says (quoting from
memory):

Just this once,
Twelve. For Rue.

Then runs
back into the woods.

How did Thresh know that Katniss had
befriended Rue?

itemprop="text">

class="normal">Answer

If I recall, as Clove
has Katniss pinned and is about to kill her, the two women share some dialog about Rue.
Thresh hears this and kills Clove.

So, to reword it, Clove
gloated about the death of Rue and Thresh overheard and killed her in his anger, but
also saved Katniss for his gratitude towards her for taking care of her since he and Rue
are both from District 11.