In the following question, a sentence has been given in Active/Passive voice. Out of four alternatives suggested, select the one which best expresses the same sentence in Passive/Active voice.
Traces of minerals have been discovered on the surface of Mars.
1
Scientists on the surface of Mars had discovered traces of minerals.
2
Minerals would be discovered on the surface of Mars.
3
Discovery of minerals has happened on the surface of Mars.
4
Scientists have discovered traces of minerals on the surface of Mars.