What are the characteristics of archaebacteria?
a. they are single cells that have a nucleus and tend to live in extreme conditions.
b. they are single cells that lack a nucleus and tend to live in extreme conditions.
c. they are single cells that lack a nucleus and tend to live in moderate conditions.
d. they are single cells that have a nucleus and tend to live in moderate conditions.

they are single cells that lack a nucleus and tend to live in extreme conditions.- B.

why is arctic sea ice important? arctic sea ice keeps the polar regions cool and moderate global climate. sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space. as sea ice melts in the summer, it exposes the dark ocean surface.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-