Read and complete the sentence with the correct part.

Today I am a member of the UN Global Education First Youth Advocacy Group. Many young people have come to me to ask how I got to be in such an initiative. It has always been a pleasure for me to share my volunteer experiences, and it is because of these experiences that I have selected out of 500 applications to serve in this group.
It all started, when I was in secondary school. I was engaged in student affairs as the president of the UNESCO club, a school platform that brings students together to discuss school matters and the pressing current issues concerning them.
After secondary school, I started volunteering within non-governmental organisations. It was at this moment that I began to understand a lot about community development. I was involved in projects and activities relating to peace, human rights and the environment. It was a great pleasure for me to contribute to the development of my community through volunteering because the impact was visible.

The author started to understand community development very well because of ...

• volunteering.
• discussing school matters.
• talking about current issues.
• engaging in student affairs.