Answer: D. The sample includes the 1,800 U.S. adults who made purchases via their mobile device
Step-by-step explanation:
The survey showed that it was based on a sample of 1,800 US adults who have made purchases via their mobile phones so D is correct.
A is incorrect because 29% of the sample is 522 people not 684. Also the sample includes more people than only those who indicated that app recommendations would drive them to add more items to their cart.
B is wrong because this is a sample so it cannot include ALL US adults who make purchases via their mobile devices.
C is also incorrect because 38% of the sample is 684 people not 522. Also the sample includes more people than those who would spend more time in the app.