Which of the following is an example that enables a store to communicate directly with consumers inside of a store, often based on the consumer$$s exact location $($e$.$g$.$ in the middle of Aisle $7,$ browsing through the $$batteries$$ section$)?$

a$.$

iBeacon

b$.$

AWS Trusted Advisor

c$.$

Real$-$time personal assistant

d$.$

In$-$window chat application