Final answer:
We categorize words like 'quick', 'shold', and 'duck' by the letter coming before 'u' in each of them, finding that 'quick' has a 'q'.
Step-by-step explanation:
The task involves observing the letter that comes before the u in each word and categorizing them accordingly. When we examine the word quick, we notice that the letter before the u is q.
Similarly, we look at the words shold and duck to identify the letters s and d, respectively, before the u. Then, we can sort these words into appropriate groups based on that criterion.