I looked on Wikipedia________.

Infinitive of purpose
We use the to-infinitive to express purpose (to answer why?):
or, in other words: We can use to + infinitive to say why we do something. It tells the other person the reason. We need to have a normal verb as well.
Examples: 
- I went on holiday (this is what I did) to relax (this is why I did it)
- He bought some flowers to give to his wife.
- He locked the door to keep everyone out.

প্রদত্ত বাক্যটির অর্থ এমন হবে: I looked on Wikipedia to find the answer.  সে উত্তরটি খোঁজার জন্য উইকিপিডিয়া দেখছে। 

সুতরাং, সঠিক উত্তর: to find the answer.

Source: Oxford Practice Grammar by J. Eastwood & British Council Learning website.