The correct option is
D Pepo
The fruit in watermelon develops from an inferior ovary in the placenta remains attached to the seeds and the outer covering is very hard. It is a type of berry known as pepo and develops from a single fertilised flower.
Syconus or sorosis develop from an inflorescence.
Balausta is a fruit with outer hard layer formed of exocarp and partially mesocarp, which also forms septa in the fruit. The endocarp covers the seeds as a papery structure and the seeds have modified fleshy testa which can be eaten.
So, the correct answer is 'Pepo'.