If I had a pen, I (write) a letter. Here the right form of verb is-

অপশনসমূহ
সঠিক উত্তর চিহ্নিত
writing
would write
will write
had written
💡
ব্যাখ্যা ও সমাধান
'Had' is in the past simple tense here (second conditional), so the apodosis requires 'would write'.