Which is the example of slime mould?

The correct option is Physarum.

To understand why, let's look at the classification and nature of each organism listed in the options:

1. What are Slime Moulds?
Slime moulds are eukaryotic, saprophytic protists. During favorable conditions, they form an aggregation called a plasmodium, which can grow and spread over several feet. Physarum is a classic genus of acellular (plasmodial) slime moulds.

2. Analyzing the Options:
• Physarum: This is a genus of slime moulds (specifically Physarum polycephalum, often used as a model organism in laboratory research). Hence, it is the correct example.
• Anabaena: This is a genus of filamentous cyanobacteria (blue-green algae), which are photosynthetic prokaryotes, not slime moulds.
• Rhizopus: This is a genus of common saprophytic fungi (such as the black bread mould) belonging to the kingdom Fungi.
• Thiobacillus: This is a genus of sulfur-oxidizing bacteria (prokaryotes) belonging to the domain Bacteria.

Therefore, Physarum is the correct example of a slime mould.