How many Surahs name is only one letter?

کتنی سورتوں کا نام صرف ایک حرف ہے؟

Four

Three

Two

Five

None of these

Three Sorahs in Quran that starts only one letter:
Surah 50 — qaaf (ق)
Surah 38 — saad (ص).
Surah 68 — nune (ن).