Lilа nоtices thаt sоme оf her co-workers leаve their lunch in the office refrigerator for several days. Not only does the office have limited refrigerator space, but the lunch leftovers also tend to expire. Lila decides to put a poster on the refrigerator, reminding her co-workers to take home their leftovers. Considering this means of communication in this situation, what channel is Lila using to transmit the message?