Sporangia of slime mould contain

The correct option is Haploid spores.

Step-by-Step Explanation:

1. Understanding Slime Moulds: Slime moulds (specifically plasmodial slime moulds or Myxomycetes) have a complex life cycle that alternates between a diploid stage and a haploid stage.
2. Plasmodium Stage: The vegetative phase of a plasmodial slime mould is called the plasmodium, which is a multinucleate, diploid ($2n$) mass of cytoplasm.
3. Formation of Fruiting Bodies: When environmental conditions become unfavorable or food is depleted, the diploid plasmodium halts its vegetative growth and transforms into reproductive structures called fruiting bodies or sporangia (singular: sporangium).
4. Meiosis in Sporangia: Inside the developing sporangium, the diploid nuclei undergo meiosis (reduction division) to produce haploid ($n$) nuclei. Cell walls are then formed around these haploid nuclei, developing them into mature spores.
5. Conclusion: Therefore, the sporangia of slime moulds contain haploid spores, which are released and dispersed by wind to germinate into new haploid amoeboid cells or flagellated cells under favorable conditions.