A. 19 June
B. 20 June
C. 21 June
D. 22 June
Explanation:
Observed annually on 21 June, the World Hydrography Day highlights the importance of hydrography and its relevance. This important day was approved and implemented by the International Hydrographic Organization (IHO) as an annual celebration. This year, the IHO is also celebrating the 100th anniversary of its formation.