a. all septated hyphae
Septate hyphae have dividers between the cells, called septa (singular septum). The septa have openings called pores between the cells, to allow the flow of the cytoplasm and nutrients throughout the mycelium.
b. all haploid nuclei
A nucleus with one set of chromosomes is called a haploid nucleus, the haploid nuclei are contained in cells of some sort and naturally a cell with a haploid nucleus is called a haploid cell.
The first step towards fusion of the nuclei is the fusion of two haploid cells and this step is called plasmogamy.
d. none of the above
Since option (c) both mating types is correct, hence this option is incorrect.