I have some duties. I must perform them

Combine the sentence using to Plus infinitive

I have some duties thereby I must perform them.

i have some duties which i must perform

And you think ... ?

(What is a "plus infinitive"?)

I have some duties.i must perform them.

I have some duties thereby i must perform them.

I have some duties, so I must perform them.

I have some duties to perform them.

He must perform his duties.

Every person has some duties. He must perform them

Every person has some duties. He must perform them.