Step 1: Meaning in IP law.
Acquiescence occurs when the proprietor of a trademark knowingly allows another to use the mark for a significant time without objection, implying consent and waiving the right to later challenge that use.
Step 2: Legal effect.
The defence bars the proprietor from obtaining injunctive relief against the user, especially when the user has built goodwill relying on the proprietor’s inaction.
Step 3: Eliminating incorrect options.
(A) No confusion is a separate defence based on absence of likelihood of confusion.
(C) Invalidity challenges the registration itself.
(D) Good faith use is another statutory defence, not acquiescence.
\[ \boxed{\text{B}} \]
Step 1: Recognising statutory defences.
Under the Trademarks Act, 1999, certain recognised defences to infringement include: Honest and concurrent use — where two parties have used the mark honestly over time.
Acquiescence — where the proprietor has knowingly allowed use over time without objection.
Fair use — descriptive use or nominative use without implying origin.
Step 2: Analysing “prior adoption and use.”
While prior use can give rise to rights (especially against later users), it is not framed as a statutory defence to infringement in the same way as the above. Prior use establishes an independent right — it doesn’t excuse infringement if the infringer’s use starts after another party’s registration and lacks lawful justification.
Step 3: Eliminating other options.
(A), (B), and (D) are expressly recognised as defences. Only (C) is not “in itself” a statutory defence — though it can be relevant in priority disputes. \[ \boxed{\text{C}} \]