The correct answer is B: may be, sharper. This is a common metaphorical expression that suggests words, especially when used maliciously or for 'backstabbing' (betrayal), can inflict deeper and more lasting pain or damage than physical weapons like a dagger. The phrase "may be" implies a possibility or potential, recognizing that while a dagger causes immediate physical harm, the emotional or reputational wounds from words can be more profound and enduring. "Sharper" in this context refers to the intensity and penetrating nature of the emotional or psychological impact.
A: should, sharper is incorrect because "should be" implies an obligation or what ought to be, rather than describing a potential or inherent capacity, which is what the proverb conveys. The statement is not about what a quill ought to be, but what it can be.
C: can, duller is incorrect because it completely reverses the intended meaning of the proverb. The essence of the saying is that words can be more potent and harmful than physical force, not less.
D: will, weaker is also incorrect for two reasons. "Will" suggests certainty, which is too strong for this metaphorical comparison, as the impact of words isn't always definitively stronger. More importantly, "weaker" contradicts the proverb's message that words can be more damaging than physical weapons.