Valid Python string literals

Question:
Which of the following statements contain valid Python string literals? Select all that are correct:

1. string = "1234"
2. string = Hello, world.
3. string = 1234
4. string = "We're #1!"
5. string = 'We're #1!'
6. string = 'Hello, world.'

Answer:
A, D, F - are the correct answers