The correct answer is weaken.
B. observe carefully
The correct answer is (A) To weaken; to reduce the force, intensity, effect, quantity, or value of. To make slender or thin; to become thin in consistency.
Attenuate comes from Latin attenuare (to make thin).
Examples of use:
- The plaintiff attenuated his case by omission of several important facts.
- Thoughtless inbreeding has attenuated the vitality of that breed.