The correct option is D Chlamydospores
In some fungi like smuts, the vegetative cells are converted into a small thick walled rounded spores known as chlamydospores. These may be terminal or intercalary in position. They remain viable for several years. On the approach of favourable conditions, they germinate to give rise the same type of mycelium. Chlamydospores are usually dark-coloured, spherical and have a smooth (non-ornamented) surface. They are multicellular, the cells being connected by pores in septae between cells. Thus, the correct answer is option B.