Aconcept map for four types of intermolecular forces and a certain type of bond is shown.

which of the following correctly identifies the intermolecular force represented by a and compares its strength relative to the intermolecular force represented by b?

a represents london dispersion forces, which are weaker than the force represented by b.
a represents hydrogen bonding, which is weaker than the force represented by b.
a represents london dispersion forces, which are stronger than the force represented by b.
a represents hydrogen bonding, which is stronger than the force represented by b.

A represents London dispersion forces, which are weaker than the force represented by B.

Explanation:

London Dispersion Forces : Intermolecular forces exist  between non-polar molecules.  They are very weak forces.  Thought to be arise from the  motion of electrons.

H-bonding: It is a special type of dipole-dipole interaction  between the H-atom in a polar bond such as N-H,  O-H, F-H and an electronegative atom such as  nitrogen, oxygen and fluorine.

It is clear that H-bonding is stronger than London-dispersion.

So, the right choice is:

A represents London dispersion forces, which are weaker than the force represented by B.

  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-