The
configuration is achieved when atoms share electrons and
form covalent bonds.

a. ideal

b. noble gas

c. electron dot

b.noble gas

Explanation:

Covalent bond:

It is formed by the sharing of electron pair between bonded atoms.  

The atom with larger electronegativity attract the electron pair more towards it self and becomes partial negative while the other atom becomes partial positive.

For example:

In water the electronegativity of oxygen is 3.44 and hydrogen is 2.2. That's why electron pair attracted more towards oxygen, thus oxygen becomes partial negative and hydrogen becomes partial positive.  Oxygen attract two electron, one by each H atom and thus complete the octet.

O₈ = 1s² 2s² 2p⁴

To complete the octet oxygen needs two electron thus it gets the electronic configuration of Neon.

While hydrogen atom need one more electron to complete the octet and gets electronic configuration of noble gas element  He.

with this one i know the answer in craters one reason i looked it up and i learned about it there is my evidence

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.