In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
Passage:

To know ______ reality, the powers of the mind need to be turned back upon itself. With concentration, the mind can ______ its innermost secrets, just as the darkest places reveal their secrets to the penetrating rays of light. We can then ______ soul truths, whether life exists for five minutes or for ______, and whether there is a God. To go beyond the mind and our present reality, we need to use the mind itself as a tool. Patanjali, in his Hatha Yoga Pradipika, stated, “Yoga is the ______ of the modifications of the mind.”