Choose all the correct statements for informal letters.

• We write informal letters to friends and relatives we know well, or to people our age.
• An informal letter should include an informal greeting such as "Hi!".
• Each paragraph should have a topic sentence.
• Informal letters should be written in a formal style.
• Short forms are used in formal letters.
• "Yours sincerely" is an informal ending.
• Phrasal verbs can be used in informal writings.