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Switching to physical lock will be a retrograde step. Digital lock provides Madhuri with an option to monitor her apartment remotely and a physical lock will not allow her to do the same. Therefore, we can eliminate option A.
We can eliminate option B too since it suffers from the same flaw as option A.
It has been given that the cleaner will be available only for a limited period every day. Therefore, the cleaner cannot be asked to explain the working of digital lock and hence, we can eliminate option C as well.
Madhuri cannot afford to be indifferent. Doing so will result in unsatisfied customers. Therefore, we can eliminate option D as well.
Option E states that Madhuri should educate her customers using a video on how to operate the digital lock. Releasing such a tutorial will ensure that the grievance of the customers get redressed. Also, Madhuri can continue using the digital lock as well. Therefore, option D is the right answer