The police have started to ________ the case.

- to এর পরে সাধারণত, verb এর basic form বসে।
- সুতরাং সঠিক উত্তর হবে: to investigate.
- পুরো বাক্যটি হবে: The police have started to investigate the case. অর্থাৎ পুলিশ, কেসটি অনুসন্ধান করা শুরু করে।

Infinitives
- It can be formed by taking a base verb and adding the word 'to' to the beginning of it.
- Infinitive phrases include the infinitive verb plus any modifiers or descriptors and can be used as a noun, adjective, or adverb.