Final answer:
Mimar Sinan, also known as Koca Sinan, was an architect, specifically the chief architect of the Ottoman Empire. There is no evidence of him being a mathematician, poet, or military strategist, though architectural work does involve mathematical knowledge.
Step-by-step explanation:
Koca Sinan, commonly known as Mimar Sinan, was a prominent figure during the Ottoman Empire era. Answering the question regarding his professions, Mimar Sinan was indeed an architect, celebrated as the chief architect of the Ottoman Empire. His architectural brilliance first came to the fore when he constructed a bridge over marshland that was proving to be an obstacle for the Ottoman Army.
Despite being of Armenian origin and beginning his life within the devshirme system, where he served as a Janissary, his talents led him to be appointed as a military engineer before eventually taking on the role of chief architect. This transition occurred when the position became vacant, and his potential was recognized, leading to his permanent diversion from the Janissary Corps.
Although there is no substantial evidence to suggest Sinan was a mathematician or a poet, his role did indeed involve some knowledge of mathematics, as it is fundamental to the field of architecture. As for his military role, as a military engineer, he would have been instrumental in designing and supervising the construction of military infrastructure, such as bridges, fortifications, and other military-related structures.
However, there is no record of him being a military strategist. To answer the student's question: a. He was an architect is true and the other options (b. He was a mathematician, c. He was a poet, d. He was a military strategist) are either not supported by evidence or refer to skills that might have been ancillary to his primary profession as an architect.