The following sentences are written in the present tense. Rewrite each sentence in each of the other five tenses.

1). I collect.
2). You split.
3). They teach.
4). We give.
5). It remains.

My answers:
1). Past: I collected Vanessa from her Seminary class.
Future: I will collect the kindling for the fire.
Present perfect: The berries I have collected will only keep a couple of days, anyways.
Past perfect: I had collected a few types of the herbs my mother had taught me to heal with.
Future perfect: I will have collected enough pine needles to make comfortable covering over the cold, hard ground.

2). Past: "I watched as you split the arrow in two," he said.
Future: You will split the final remains of the greens and smoked fish equally.
Present perfect: I've noticed you have split away from your group.
Past perfect: You had split the cake already.
Future perfect: You will have split your pants by now, if I hadn't sticked them.

3). Past: They taught about many historical events.
Future: They will teach about Greek Mythology the following week.
Present perfect: They have taught serveral children to swim this summer.
Past perfect: They had taught about the different types of stars in the Astronomy class.
Future perfect: They will have taught the entire subject by the end of the year.

4). Past: We gave donantions to the orphanage.
Future: We will give our graditude at the ceremony.
Present perfect: We have given them several oppurtunities to prove themseleves trust-worthly.
Past perfect: We had given them our last bit of food.
Future perfect: I will have given my life to save his own.

5). Past: It remained a mystery to where you had disappeared to.
Future: It will remain your duty to choose which side you stand to fight for.
Present perfect: It has remained a sacred monument for over a decade.
Past perfect: It had remained submerged in the deep depths of the ocean for decades.
Future: It will have remained undiscovered if not for the sudden erosion.

Great job on your answers! Here's an alternative approach to rewrite the sentences in each of the five tenses:

1. Simple Past: I collected the mail this morning.
Future: I will collect the package from the post office tomorrow.
Present Continuous: I am collecting items for the charity drive.
Past Continuous: I was collecting shells on the beach when the storm hit.
Future Continuous: I will be collecting data for the research project next week.

2. Simple Past: You split the wood for the fire last night.
Future: You will split the bill with your friend at the restaurant.
Present Continuous: You are splitting the workload evenly among the team members.
Past Continuous: You were splitting your time between work and studies in college.
Future Continuous: You will be splitting your vacation between two destinations.

3. Simple Past: They taught English to foreign students last semester.
Future: They will teach a painting class next month.
Present Continuous: They are teaching a math lesson to the seventh graders.
Past Continuous: They were teaching a dance routine when the lights went off.
Future Continuous: They will be teaching a cooking workshop at the community center.

4. Simple Past: We gave flowers to our teacher on Teacher's Day.
Future: We will give a presentation at the conference next week.
Present Continuous: We are giving a hand to our neighbors with their move.
Past Continuous: We were giving our best effort during the sports competition.
Future Continuous: We will be giving out free samples at the product launch event.

5. Simple Past: It remained untouched for years until you found it.
Future: It will remain a timeless classic for generations to come.
Present Continuous: It is remaining a challenge to solve this puzzle.
Past Continuous: It was remaining a secret until the truth came out.
Future Continuous: It will be remaining a popular tourist destination in the future.

Are my answers correct?

Excellent.

The only mistake is in the last one. That sentence should read, "It WOULD have remained undiscovered if not . . . "

How about --

Next June, Josie and I will have remained friends for a decade.