Which sentence is written in active voice?

*
First prize at the science fair was presented by the mayor.
The scientists discovered a new way to fight the common cold.
The famous ice cream shop was owned by Angel's grandfather.
The best essay was written by the newest student in class.

The scientists discovered a new way to fight the common cold.

What is the best way to change this sentence from passive voice to active voice?

The audience was moved to tears by the beautiful voices of the choir.
*
Of the choir, the audience was moved to tears by the beautiful voices.
To tears, the audience was moved by the beautiful voices of the choir.
The tears of the audience were moved by the beautiful voices of the choir.
The beautiful voices of the choir moved the audience to tears.