Answer: B) process.
Step-by-step explanation: a colon is a punctuation mark that is used to mark a major division in a sentence, to indicate that what follows is an elaboration, summation, or implication of what precedes. In the given sentence the quote "I clear my mind, gather my materials, and quiet my space" is elaborating or explaining what the painter's process was, so it should be a colon after the word "process."