Choose the correct time form. Nina studied English for 2 years. Birds are already flying south. They knew him for many years. Mike forgot to learn the poem. The children watched cartoons for 2 hours. The train has just arrived. We did not have a holiday for 5 years. She taught at this school for twenty years. David drew in his studio from 10 o'clock. Mary and Sam collected the stamps for 3 years. Since childhood, their parents have been friends. Dave was a student for 2 years.