What is a word cloud?

$$ a$.$ It involves having a discussion with all members of a group where everybody gives their idea in simple words.

O b$.$ A simple tool to visualize the voice of a company's customers where larger sized words indicate more salient elements.

O c$.$ A visualization tool to displays words bases on who said what first, the first words to be said are the largest ones.

O d$.$ A technique to come up with synonyms of words that will better suit the copy of an advertisement.