What is the difference between an arc and a segment when drawn with the ellipse tool?

Need some ! asap i need to figure out 3 major changes in bridges over time and why these changes to adapt to both improvements in technology and changing social links would also alot.

Culinary arts- a serving of seafood appetizers is arranged on a bed of ice. dipping sauces are in the center with a tiny spoon for dishing them out. what technique did the chef apply to make the arrangements? the chef applied the technique to make the arrangements

What do i do if i want to hit someone with a bus