The correct option is
B Real
Accounts relating to properties or assets are known as "Real accounts". A separate account is maintained for each asset. E.g. Cash, Machinery, Building, etc. Real accounts can be further classified into tangible and intangible.
1. Tangible Real Accounts: Theses accounts represent assets and properties which can be seen, touched, felt, measured, purchased and sold. For e.g. Machinery account, Cash account, Furniture account, etc.
2. Intangible Real Accounts: These accounts represent assets and properties which cannot be seen, touched or felt but they can be measured in terms of money. For e.g., Goodwill accounts, Patents accounts, etc.
Patent account is anaccount whose value can be measured in terms of money and treated as an asset of the business, hence, is classified as a real account.