The question asks us to match the organizations listed in List-I with their corresponding headquarters in List-II. Here is a breakdown of the options:

Option 1: UNESCO - It is known as the United Nations Educational, Scientific, and Cultural Organization. The correct headquarters for UNESCO is Paris.

Option 2: IMF - It stands for the International Monetary Fund. The correct headquarters for the IMF is Washington, D.C.

Option 3: ILO - It stands for the International Labour Organization. The correct headquarters for the ILO is Geneva.

Option 4: UNIDO - It stands for the United Nations Industrial Development Organization. The correct headquarters for UNIDO is Vienna.

Now let`s match the options in List-I with their corresponding headquarters in List-II:

(a) 2 1 4 3 - This option matches the correct headquarters for each organization.

(b) 2 4 1 3 - This option mixes up the headquarters for UNESCO and UNIDO.

(c) 3 1 4 2 - This option mixes up the headquarters for IMF and UNIDO.

(d) 3 4 1 2 - This option mixes up the headquarters for ILO and UNESCO.

The correct answer is (a) 2 1 4 3