I knew his name (Complex).
I know what is his name.
I know what his name was.
I know what was his name.
I knew what his name was.
সঠিক উত্তর:
I knew what his name was.
ব্যাখ্যা ও নোট:
Simple বাক্যের object (his name) কে noun clause (what his name was) করে Complex করা হয়েছে এবং Past Tense ঠিক রাখা হয়েছে।