Extracted from an English cloze test:
.....these virtual selves exist in the same online spaces that many people use every day. And this is a new and unfamiliar phenomenon that some people might find___________ -- previously dead people were not present in this way.
- be troubled
- to trouble
The answer is 3 because the key said find troubling stands for find it to be troubling, but I don't understand why it stands for that. I want to know what grammatical topic is related to this sentence.