"was discovered" - was discovered, the form "Past Simple Passive" is used to describe an action performed on the object in the past. Translation: Gravity was discovered by Isaac Newton - Gravity was discovered by Isaac Newton.

"discovered" - discovered, the form "Past Simple" is used to describe a completed action in the past. Translation: Marie Curie discovered radium and polonium - Marie Curie discovered radium and polonium.

"had studied" - had studied, the form "Past Perfect" is used to describe an action that happened before another action in the past. Translation: Scientists had studied DNA - Scientists had studied DNA.

"was being developed" - was being developed, the form "Past Continuous Passive" is used to describe an action that was happening in the past and was performed on the object. Translation: The vaccine was being developed - The vaccine was being developed.

"have been discovered" - have been discovered, the form "Present Perfect Passive" is used to describe actions completed by the present moment. Translation: Planets have been discovered - Planets have been discovered.

"are used" - are used, the form "Present Simple Passive" is used to describe a regular action performed on the object. Translation: Telescopes are used - Telescopes are used.

"will have been developed" - will have been developed, the form "Future Perfect Passive" is used to describe an action that will have been completed by a certain point in the future. Translation: Technologies will have been developed - Technologies will have been developed.