Chittering Rats who chooses the card to put

[Kerdo]

if I play a Chittering Rats, who chooses what card opponent will put on library, me or opponent? the card forgot to say

[Arix]

No, the card didn't forget to say. The opponent does it.

[DatAsh]

When Chittering Rats enters the battlefield, target opponent puts a card from his or her hand on top of his or her library.

It literally could not be any more clear.

[Kerdo]

I know who puts but not sure who chooses which card? because I cast the spell?

[DatAsh]

...How is this most basic wording confusing you? If you got to choose the card, it would explicitly say "of your choice".

[Kerdo]

so you mean he chooses it right? ok

Only reason I was unsure is since I am the one casting the spell so in some way it would've made sense for me to pick the card since its my spell I am the one paying the mana and stuff