Solution:(d) The lion asked the lioness where she would hide herself, until he returned. (Correct)(a) The lion asked the lioness whether she would hide herself. until he returned. (Whether is used instead of where)
(b) The lion asked the lioness where she will hide herself, until he
returns. (Change of tense to simple future is incorrect.)
(c) The lion asked the lioness where would she hide herself, until he returned. (Change of reported speech to interrogative sentence is incorrect.)