The organic matter in humus is made of
a.
dead worms
c.
roots
b.
stems
d.
all of the above

The correct answer is option (d).

Explanation:

Humus is component of the soil formed from the decomposition of dead plants (leaves, flower, roots. stems etc)and animal matter by the action of micro-organism. This makes the soil nutrient rich and fertile for plants.

Hence, the correct answer is (d).

the answer

explanation:

the capillary tube was too close to the bottom of the beaker.

the ruler may have moved.

water got into the capillary tube.

the temperature was not allowed to equilibrate in the 2-4 minutes.

  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-