H. Imagine that you and your friend get a chance to visit another planet. There, you befriend an alien who takes you around the planet. After reaching the earth, write a letter thanking him for all the help he did.
We landed on the earth safely. It was an amazing experience to travel in space. My friend and I were very lucky to be a friend of you in the strange planet. We felt at home after meeting in the new planet. But for your help, we could not have made our visit a success. We are very thankful to you for your friendship and entertainment. We have enough confidence to make another visit there as you are there to host us. We are heartened to feel that we are not alone in the universe. We are sure that you are friendly beings, as we have observed you all. We invite you to visit us. Please come and live among us and share your wisdom with us. We do really need it. If you come to earth, I am sure that you would like it. On behalf of all humanity I welcome you to Earth.
Looking forward to your early arrival.