What is the pronunciation aid that determines the stress placed upon a syllable called?

What is the main purpose of a speech bubble in a graphic novel ?

Question 3 of 10 points which sentence is an example of chronological structure in "the city without o a. without daily pumping, manhattan's subway tunnels would be flooded o b. some time in the next 100,000 years, glaciers will cover all of manhattan o c. central park has a garden that houses plants mentioned in shakespeare's plays. o d. if flooding were to go unchecked, steel support beams in buildings would rust

Which big-picture idea comes logically from these details?