The C-Gear has a feature where you can answer survey questions for you to share the answers of which through the C Gear's Passing By mode. In Castelia City, you'll find the C Gear building to the far left of the Main Area. In this building, a researcher will set you various questions for you with a variety of excuses for giving you the questions. You need to do them all sequentially with the questions ranking up as you go. If you manage to successfully complete the surveys through Passing By, you'll get given an item. You get given a choice on whether to do the surveys by the amount of people or within a set amount of time.
The way you collect answers is simple. In the C Gear Passing By mode, you yourself answer the questions, just as the other players do. Then, when you encounter the players in Passing By mode, the information will be shared automatically and you wont need to go and request the information. There isn't a set time limit on how long you have to run the surveys, but you have a limit before you can produce results
The questions have not changed since Black & White, those the first one has been adapted to focus solely on Pokémon Black 2 & White 2.