𝐖𝐡𝐚𝐭 𝐢𝐬 𝐭𝐡𝐞 𝐜𝐨𝐫𝐫𝐞𝐜𝐭 𝐬𝐞𝐧𝐭𝐞𝐧𝐜𝐞?

𝐀. Studying for the exam took me all night. 
𝐁. To study for the exam took me all night.
𝐂. Study for the exam took me all night.
𝐃. The studying for the exam took me all night.