The unicellular algae used to supply and regulate the oxygen in space programmes is

Spyrogyra
Chlorella
Ulothrix
Odogonium

The correct answer is B. Chlorella.

Chlorella is a unicellular green algae that is used to supply and regulate the oxygen in space programmes. It is a simple organism that can grow in a variety of environments, including in space. Chlorella is a good source of oxygen, and it can also be used to produce food and other products.

Spyrogyra is a filamentous green algae that is not used in space programmes. It is a simple organism that can grow in a variety of environments, but it is not as well-suited for space travel as Chlorella.

Ulothrix is a filamentous green algae that is not used in space programmes. It is a simple organism that can grow in a variety of environments, but it is not as well-suited for space travel as Chlorella.

Odogonium is a filamentous green algae that is not used in space programmes. It is a simple organism that can grow in a variety of environments, but it is not as well-suited for space travel as Chlorella.

Chlorella is a good choice for space programmes because it is a simple organism that can grow in a variety of environments, including in space. It is also a good source of oxygen, and it can be used to produce food and other products.