Give the theory of the past progressive tense?

My friend’s name is Peter and he loves music. He is good at (1) _____ and he can play the guitar. He wants to learn the (2) _____ when he is a bit older. He is already in a (3) _____ and they hope to play at the school (4) _____ next term. He is also interested in (5) _____ so his favourite (6) _____ at school is (7) _____. But to be honest, he can’t wait to leave school and become a (8) _____.

Skateboarding (1) _______ back to the 1940s and 1950s in California as a replacement to surfing waves in unfavorable weather conditions. The (2) _______ of the first skateboard was unknown. However, one thing was known for sure. The first skateboard was made from wooden boxes or boards with roller wheels on the bottom. Skateboarding reached its (3) _______ in the early 1960s. Then it lost its attraction towards the end of the decade. Numerous improvements have been made to skateboards (4) _______ safety reasons. Millions of teenagers (5) _______around the world now.

The Nutcracker is a classical ballet. It is based on a fairy tale named "The Nutcracker and the Mouse King" by E.T.A. Hoffmann. The ballet tells of the adventure of a little girl to the Land of Sweets on Christmas Eve. The first performance of the ballet was on 18 December 1892. It was not very successful in the first years. The ballet became more popular after Walt Disney's use of its music and its show on television in the 1950s. Nowadays, The Nutcracker ballet is a must-see at Christmas.

1. The Nutcracker comes from a novel.

2. The main character of The Nutcracker is a boy.

3. The Nutcracker was first performed before Christmas in 1892.

4. The Nutcracker was a quick success.

5. The Nutcracker is very popular now.