May I know how to remove the arc as shown in the picture below without touching the text?
Sometimes I prefer not to remove construction lines such as this, but to change them to no outline. This means they do not display or print, but if you want a subsequent edit that needs the curve, it is still there.
Like Harry and Anand said; try to avoid removing the path if possible. If you do, I advice you to convert the text to curves first.This to avoid unpleasant surprises if you open the file in the future. There's no guarantee future versions will interpret the text with 100% accuracy (may be depending on software upgrades, OS upgrades or font updates) and the text may end up in the wrong place or look completely different.
If you still want to remove the line after reading this: Simply click the line twice (first time selects text and line, second selects line only) and delete it.
Here's what I'd do to eat the cake and still have it: Create a new page with all your objects (Duplicate page with layers and content) and convert all effects, and things like text on a path, to curves. Keep the first page untouched for future editing.