Spirochaetes are ...

Which of the following may occur in arctic and alpine meadows?

The membrane of which one of the following microorganisms is three-layered?

Given below are two statements. Based on them,select the correct option given below.
Statement $I$: $N_2$ fixing heterocystic cyanobacteria is Anabaena.
Statement $II$: $N_2$ fixing Anabaena is symbiotic with lichens.

Spirochetes are .......

Match the organisms in Column-$I$ with habitats in Column-$II$.

Column-$I$	Column-$II$
$(a)$ Halophiles	$(i)$ Hot springs
$(b)$ Thermoacidophiles	$(ii)$ Aquatic environment
$(c)$ Methanogens	$(iii)$ Guts of ruminants
$(d)$ Cyanobacteria	$(iv)$ Salty area

Select the correct answer from the options given below: