Agroup of very small, pleomorphic bacteria without cell walls, previously thought to be viruses, because they are capable of crossing bacterial filters.
a) mycoplasma
b) clostridia
c) anthrax
d) spirochetes

A) Mycoplasma

Explanation:

This kind of bacteria does not have a cell wall.

This is why it's so difficult to kill them with antibiotics that block cell wall synthesis like penicillin. They do not respond to them.

Atypical pneumonia and some pelvic inflammations are caused by this kind of bacteria.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.