Section 25 Patents Act 1970 deals with 'opposition to grant of patent'. Pre-grant opposition under Section 25(1) may be filed:

1. Section 25(1) Patents Act 1970: 'Where an application for a patent has been published but a patent has not been granted, any person may, in writing, represent by way of opposition to the Controller against the grant of patent on the grounds [listed in clauses (a) to (k)]'. 2. The pre-grant opposition is free (no fees) and any person may file it. 3. Grounds include: wrongful obtaining; prior publication; prior claim; prior public knowledge or use; obviousness; not invention per Sections 3-4; insufficient description; non-disclosure or wrong disclosure of source of biological material; etc. 4. Section 25(2) provides for POST-GRANT opposition within 12 months of grant by any person interested. 5. Hence option A is correct. _Source: Patents Act 1970 / Copyright Act 1957 / Trade Marks Act 1999 (Bare Acts, IPIndia portal + Copyright Office) — Patents Act 1970, Section 25(1)_