The first regular English tragedy Gorboduc contains 5 acts, while the first 3 acts were written by Thomas Norton, identify the author who wrote the remaining 2 acts.

The correct option is Thomas Sackville.

To understand why this is the correct answer, we can break down the history and structure of the play:

1. Background of the Play:
Gorboduc, also known as Ferrex and Porrex, is widely recognized as the first regular English tragedy. It was first performed during the Christmas revels at the Inner Temple in London in 1561 and later performed before Queen Elizabeth I on January 18, 1562.

2. Structure and Versification:
The play is structured in the classical Roman model of 5 acts and is famous for being the first English drama to employ blank verse (unrhymed iambic pentameter).

3. Division of Authorship:
The tragedy was a collaborative effort between two writers:
- Thomas Norton wrote the first three acts (Acts 1, 2, and 3).
- Thomas Sackville (Lord Buckhurst) wrote the final two acts (Acts 4 and 5).

Therefore, Thomas Sackville is the author who wrote the remaining 2 acts of the play.