Final answer:
Mr. Johnson is the correct answer as he is portrayed as a figure who supports and solidifies alliances.
Step-by-step explanation:
The correct answer is a. Mr. Johnson. In the provided reference texts, Mr. Johnson is shown to be a supportive figure who takes a deep and lively interest in the welfare of others, notably in the context of abolitionism. He is the one who would likely offer his hand to both Charlie and the speaker in a gesture symbolizing the solidification of an alliance. The texts paint a portrait of a figure concerned with the wellbeing and advancement of those around him, mirroring the implication of the question that a character is reaching out in a supportive and unifying manner.