Please answer the following question by reasoning step-by-step.
Mal would cover the whole at night, but he always left a what for his cats?\nOptions:\n- underneath\n- opening\n- closing pots and pans\n- medium\n- leave open

opening
Opening means to move a door or window so as to leave a space allowing access and vision.

Mal would cover the whole at night, but he always left an opening for his cats.

.

The answer: opening