Fruit of peanut is
A. Pods develop underground, an unusual feature known as geocarpy. After fertilization, a short stalk at the base of the ovary (termed a pedicel) elongates to form a thread-like structure known as a "peg". This peg grows down into the soil, and the tip, which contains the ovary, develops into a mature peanut pod.
B. Achene- A small, indehiscent, one seeded fruit developing from a monocarpellary ovary and in which pericarp is hard, leathary and remains free from seed coat. E.g. Mirabilis.
C. Caryopsis- A small, indehiscent, one seeded fruit developing from a monocarpellary ovary and in which pericarp is fused with the seed coat. E.g. Wheat.
D. Drupe- A small, indehiscent, one seeded fruit developing from a monocarpellary ovary and in which pericarp is differentiated into outer,thin epicarp, middle fleshy and fibrous mesocarp and inner hard and stony endocarp. E.g. Mango. So, the correct answer is 'Pod'.