“Researchers ___ a new vaccine last year.”

Solution: “developed” (Past Simple) because the action is completed at a specific past time (“last year”).

Rule: Use Past Simple (V2) for completed actions in the past.

“Water ___ (boil) at 100°C under normal pressure.”

Solution: “boils” (Present Simple)

Rule: Use Present Simple for scientific facts and general truths.

“The team publishes their findings next month.”

Solution: “The team will publish their findings next month.”

Alternative: “The team is going to publish…” (for planned future actions)

“By 2025, scientists ___ a cure for this disease.”

Solution: “will have found” (Future Perfect)

Rule: Use Future Perfect (will have + V3) for actions that will be completed before a specific future time.

“When the results were published, the team already moved to new research.”

Solution: “When the results were published, the team had already moved to new research.”

Explanation: The “moving” action happened before “publishing”, so we use Past Perfect (had + V3).

“Right now, the researchers ___ (analyze) the data from the experiment.”

Solution: “are analyzing” (Present Continuous)

Rule: Use Present Continuous (am/is/are + V-ing) for actions happening now.

“After the scientist ___ (finish) the experiment, she ___ (write) a report.”

Solution: “had finished” (Past Perfect) and “wrote” (Past Simple)

Logic: The experiment was completed before writing the report.

“Our team is making important discoveries,” the scientist said.

Solution: “The scientist said that their team was making important discoveries.”

Changes:
1. Pronoun (our → their)
2. Tense (is → was)
3. Added “that”

“The researchers ___ (work) on this project for three years before they made a breakthrough.”

Solution: “had been working” (Past Perfect Continuous)

Rule: Use Past Perfect Continuous (had been + V-ing) to emphasize duration before another past action.

“Scientists ___ (discover) a new planet last month. Right now, they ___ (study) its atmosphere. By next year, they ___ (collect) enough data to draw conclusions.”

Complete Solution:
“Scientists discovered a new planet last month. Right now, they are studying its atmosphere. By next year, they will have collected enough data to draw conclusions.”

Analysis:
1. Past Simple (completed action)
2. Present Continuous (current action)
3. Future Perfect (action completed before future time)