Since then many countries and nongovernmental organizations ..... (Celebrate) this day

Since then many countries and nongovernmental organizations ..... (Celebrate) this day worldwide each year
Promotion ..... (Activity) for this day traditionally include the distribution of printed materias, such as calendars fact sheets, posters and postcards, to educational institutions and the general public. There may also be forums or discussions on drought and desertification,.... (they) influence on society and ways to minimize tge problem