When $cocci$ bacteria are present in a bunch or cluster,they are called:

Given below are two statements:
Statement $I$: Mycoplasma can pass through less than $1 \ \mu m$ filter size.
Statement $II$: Mycoplasma are bacteria with cell wall.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following statements is not correct for methanogens?

Statement-$I$: Nuclear membrane is absent in bacteria.
Statement-$II$: Methanogens are responsible for the production of methane.

Match the following columns:

Column-$I$	Column-$II$
$A$. Halophiles	$i$. Gram-negative bacteria
$B$. Thermoacidophiles	$ii$. Extremely salty areas
$C$. Spirochetes	$iii$. Responsible for methane production
$D$. Firmicutes	$iv$. Acidic and high temperature environments
	$v$. Gram-positive bacteria

What is true for Archaebacteria?