Explanation
electrovalent bond

 a chemical bond formed between ions of opposite charge. — called also ionic bond. —distinguished from covalent bond.

"C"

Explanation:

A system administrator is a person that maintains ,configures and ensure a reliable function of a computer system. He monitors the performance , functionality  , resources and security of a computer system to meet the needs of users.

In his function as an administrator , he regularly acquire or update computer component , designs and functions using various techniques and approach to ensure that a computer meet the need of the users and the organization.

The approach adopted to resolve issues are relative to the issues to be corrected . In the situation where an existing account has to be kept away from new users , the best approach approach. is to remove the customer record type as an Assigned record type in the user's profiles and permissions setting