Fill in the blank with the appropriate verb form. We ________ nothing…

The correct answer is Option (4) → have learnt

Present perfect tense:

• We use have/has + past participle (V3) for a period of time that runs from the past up to now.
• Clue word: "So far" means up to now.
• It goes with the present perfect.
• Complete sentence: We have learnt nothing from the mistakes of our ancestors so far.

Why the Other Options are Incorrect?

Option 1: are learning — Incorrect.

• "Are learning" is the present continuous.
• It shows an action going on at present.
• "So far" asks for the result up to now.
• Example: We are learning French this year.

Option 2: had learnt — Incorrect.

• "Had learnt" is the past perfect.
• It shows an action finished before another past action.
• There is no second past action here.
• Example: I had learnt to swim before we moved to Goa.

Option 3: learnt — Incorrect.

• "Learnt" is the simple past.
• It is used for a finished time in the past, like "last year".
• "So far" joins the past to now.
• Example: Amit learnt to drive last summer.