The effect of the word "babble" in the line "O thirty million English that babble of England's might" is best captured by:
D) It directly accuses the audience of inaction.
The use of "babble" suggests a trivial or meaningless conversation, implying that the citizens are talking aimlessly or without serious thought about the actual significance or consequences of England's might, which can be seen as a critique of their inaction in the face of more serious issues, such as war or conflict.