A common sedimentary rock made of tiny grains of clay is: limestone
shale
slate
granite

Shale is one of the most common sedimentary rocks. It is composed of silt or clay that has been compacted or squeezed together to form a solid rock. Shale is usually found in thin layers. The silt or clay that composes shale is made of very small pieces of weathered rock.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

  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-