• Over the past few decades, space exploration has revolutionized our understanding of the universe, yet many mysteries remain unsolved.

• Past Perfect

• Present Perfect Continuous

• Present Perfect

• Simple Present

• The soldiers were advancing toward the enemy's stronghold when a sudden change in weather forced them to retreat.

• Past Continuous

• Past Perfect

• Past Perfect Continuous

• Present Simple

• The researchers had been studying the effects of climate change for years before they published their groundbreaking findings.

• Present Perfect

• Past Simple

• Future Simple

• Past Perfect Continuous

• As technology continues to evolve, the way we communicate has changed dramatically over the last decade.

• Past Continuous

• Present Simple

• Future Perfect

• Present Perfect

• By the time the team arrived at the stadium, the match had already started, leaving them no chance to warm up.

• Past Perfect

• Future Simple

• Present Perfect Continuous

• Past Simple

• As the sun set over the horizon, the hikers realized they had lost their way in the dense forest.

• Past Continuous

• Past Perfect

• Future Simple

• Present Perfect

• The scientists had conducted numerous experiments before they finally discovered a viable solution to the problem.

• Past Simple

• Future Perfect

• Present Simple

• Past Perfect Continuous

• While the students were preparing for their exams, unexpected news about the school closure disrupted their focus.

• Past Continuous

• Past Perfect

• Simple Present

• Present Perfect

• As the storm approached, the sailors were preparing their ship for the rough seas ahead.

• Past Continuous

• Past Perfect

• Present Perfect

• Future Simple

• The students had been studying diligently for weeks before they finally took their final exams.

• Present Perfect

• Past Simple

• Future Simple

• Past Perfect Continuous