Explanation:

- Let's examine the passage.

- John was an artist (1) by profession. He initially pursued his interest in art.

- He was very (2) at his work, indicating skill and talent.

- He could (3) any subject he thought of, showcasing his creative ability.

- Due to circumstances, he was forced to change his approach.

- Now, let's consider the provided options for blank (5):

- Option 1: duplicating - Completing or making copies of the work of renowned artists.

- Option 2: dominating - Doesn't fit as it's about taking control, not the context here.

- Option 3: doubting - Unrelated to the context of altering artistic style.

- Option 4: doubling - Irrelevant as it means to increase by two times.

- The best option is Option 1: duplicating, as it aligns with the context where John replicated works of famous artists.

- Option 1: duplicating is indeed the correct choice.