Question

On a game show, Elena is given the choice of three doors: Behind one door is the Grand Prize; behind the others, consolation prizes. She picks Door A, and the host, who knows what is behind each door, opens Door B, revealing a consolation prize. The host then offers Elena the opportunity to change her selection to Door C. What should she do?

Answer 1

She should keep her selection of Door A, if its the door she wants, then the Host should open the door for her

Hope this helps :)

Answer 2

From the very beginning, each door had a 1/3 probability chance to be holding the grand prize. And the fact that she saw the consolation prize behind one of them does not change this probability.
From the beginning, all doors had equal chances.

Based on this, the answer to your question would be:
She could either accept or not accept the host's offer because the probabilities of the three doors were equal from the beginning.