Answer:
b. chastise the church for adopting a passive role in the world
Explanation:
Martin Luther King Jr in this excerpt is calling out the present day Church for this indecisive stance and passivity in the society.
He did this by comparing the early Church and present Church. In his words, the early Church were active speakers of the truth and an instrument of change, a "thermostat that transformed the mores of society" and not merely a thermometer.
He also pointed to the fact that when the early Church entered a new location, they were soon noticed by the influential "power structures" who sought to convict them as they were agitators but when compared to the present church, they are in stark contrast as they are passive and indecisive in lending their voices to issues in the society and as such the influential members of the society disregard them and continue to perpetrate evil.