Final answer:
The word that fits the context of making slight changes to improve something is 'adjust'. Options such as 'modify', 'adapt', and 'shift' imply more significant changes or changes for different purposes.
Step-by-step explanation:
You could adjust your TV antenna, your thinking, or the collar of your shirt. When you readjust something, you make slight changes again and again until you get it right. The correct answer is C. adjust. The act of making slight modifications to achieve the desired position, understanding, or arrangement is referred to as adjusting. On the other hand, to modify (option A) generally implies making more significant changes, adapt (option B) means to change something to suit a new purpose or situation, and shift (option D) typically means to move slightly to a new position. Therefore, the most fitting word to use in this context is 'adjust'.