Step 1: Understand ethics in research.
- Ethics demands honesty, transparency, avoidance of bias, and prioritizing the client's genuine needs over profit-making motives.
Step 2: Evaluate each statement.
- (a) TRUE: Full disclosure by client is necessary for accurate problem definition.
- (b) FALSE: The researcher is not ethically bound to offer the most expensive services — instead, they must offer the most suitable and cost-effective approach. This statement violates ethical principles.
- (c) TRUE: Hidden motives compromise the integrity of problem definition.
- (d) TRUE: The researcher must work in the client’s best interest within ethical limits.
\[
\boxed{(b)}
\]