The correct answer is weaken.
The correct answer is (B) To weaken (in force or effect); to water down (doctrine, zeal, story, etc.); to reduce strength of (fluid); to diminish brilliance of (color); to make less concentrated by adding more water or a thinner, etc.
Dilute comes from Latin diluere (to wash away).
Examples of use:
- He added water to the reagent to dilute its strength.
- Their argument has been diluted by the discovery of the missing papers.