Blue-green algae (Cyanobacteria) contain which type of chlorophyll?

An organism lacking chlorophyll but able to carry on photosynthesis of organic matter has been found among which one of the following?

Which one is the smallest organism capable of autonomous growth and reproduction?

What is the habitat of halophiles?

Which of the following cyanobacteria can fix atmospheric nitrogen?
$I.$ Anabaena
$II.$ Oscillatoria
$III.$ Nostoc
Choose the correct option.

Cyanobacteria and heterotrophic bacteria have been clubbed together in eubacteria of kingdom-Monera as per the 'five kingdom classification' even though the two are vastly different from each other. Is this grouping of the two types of taxa in the same kingdom justified? If so,why? Discuss the cellular composition of cyanobacteria and heterotrophic bacteria that make them introduced in eubacteria.