In deficit condition of Balance of Payment if the central bank sells foreign exchange then this particular transaction is known as.......

The correct option is Official reserve sale.

Detailed Explanation:
The Balance of Payments (BoP) is a systematic record of all economic transactions between the residents of a country and the rest of the world during a given period. A BoP deficit arises when the total autonomous payments (outflows of foreign exchange) exceed the total autonomous receipts (inflows of foreign exchange).
To bridge this deficit and restore equilibrium, the central bank of the country must intervene.

The central bank holds the country's official reserves of foreign exchange and gold. When there is a deficit, the central bank sells foreign exchange from these reserves in the foreign exchange market to meet the excess demand for foreign currencies. Since this transaction involves drawing down the official reserves of the central bank, it is termed as an official reserve sale (a type of accommodating transaction).

Let us look at why the other options are incorrect:
1. Portfolio Investment: This refers to investment by foreign entities in the financial assets (like shares and bonds) of a country, which is an autonomous capital account transaction, not a corrective action taken by the central bank.
2. Net Invisibles: This is the difference between the value of exports and imports of invisible items (like services, transfers, and income flows) on the Current Account.
3. Net factor income: This is the difference between the factor income earned from abroad by normal residents and the factor income paid to foreign residents.