Methanogens belong to

An organism that performs photosynthesis but does not release any molecular oxygen during the process is:

The difference between Gram-positive and Gram-negative bacteria is due to the:

Pili in bacteria represent

Plant pathogenic bacteria are usually ..........

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: