Question

why did megan add bumpy lines and a string to her tick tool? to make the bottle easier to find to make the tick tool easier to build to make the glue easier to hide to make the tick tool easier to use

Explanation:

The bumpy lines and string are likely added for functional improvement. Bumpy lines could provide a better grip (making it easier to handle), and a string might aid in maneuvering or positioning (enhancing usability). The other options (finding the bottle, building ease, hiding glue) are less relevant to typical tool - enhancement rationales focused on usability.

Answer:

to make the tick tool easier to use