Which of the following phonetic proximity pairs is legally excused from invalidating the prayer if substituted?

Errors in Recitation (زلّة القارئ)

• Alif (أ) and Ya (ي).
• Sad (ص) and Seen (س), or Ta (ط) and Ta (ت).
• Kaf (ك) and Noon (ن).
• No letter substitutions are ever excused.