Which feature is common between methanogens and halophiles?

In which of the following organisms are hormones normally absent?

Methanogens are most abundant in a

Consider the following four statements $(A-D)$ and select the option which includes all the correct ones only.
$(A)$ Archaebacteria differ from other bacteria in having a different cell wall structure.
$(B)$ Bacteria as a group show the most extensive metabolic diversity.
$(C)$ All Eubacteria have chlorophyll ' $a$' pigment similar to green plants.
$(D)$ Mycoplasma can survive without oxygen.

Mycoplasma is:

Which of the following is an example of a Gram-positive bacterium?