My Critical Reasoning:

When you need to base on certainty of knowledge, where you turn to?
Science!
Well, science changes with new findings. That’s what really science is, honest and truth (though the corrupt scientists always twisted the science and stupid cattle-minded people took that for granted). For example, science once said Sun was the center of the universe. And this has been contentiously happening for health and many other issues.
Then when we are in dispute about issues in life where we turn to?
Constitution of a country or the constitution of the United Nations I guess
But that also goes on changing with new situations, times, ideologies.
Then we turn to the books revealed from God?
That’s a good idea. The creator of the universe has the ultimate knowledge of everything. But most of those books has been changed by people.
What about Al-Quran!
That’s the point! When all other books that people claim inspired or revealed by God but has gone through numerous changes by people therefore you cannot turn to them for certain knowledge.
But the Quran is stand aside from that corruption. It is today as it was revealed 1400 years ago by the creator of the universe. It is preserved by the ONE who sent it
69:51

وَإِنَّهُ لَحَقُّ الْيَقِينِ

Sahih International

And indeed, it is the truth of certainty.

Bangla

নিশ্চয় এটা নিশ্চিত সত্য।