What overall structure do these two passages share?

a.

problem/solution

b.

question/answer

c.

chronological

d.

comparison

story:

passage 1

bridges—then and now

bridges are structures with a roadway or a path. they are found across areas such as valleys, mountains, lakes, and rivers. people use bridges to cross over from one side to the other. bridges connect one part of a city or town with another. they enable people to reach others to exchange ideas.

in ancient times, people used wooden logs, stones, and dirt to build bridges. as a result, they could build bridges only over small, open spaces. moreover, because of the materials used, these bridges were not strong. when it rained, rainwater washed away all the dirt and the mud that was used to hold the bridge together. this left people stranded for several days and sometimes for months.

gradually, people realized that bridges needed to be strong and sturdy enough to support their own weight and also the weight of the people and vehicles that traveled on them. in addition, bridges needed to hold out against strong winds and heavy storms.

to build stronger bridges, people experimented with various materials. people in ancient rome discovered that crushed and grounded rocks from volcanoes could be used to build bridges. when mixed with water, the powdered volcanic rock cemented the materials together, and even today, people use a similar substance called mortar for construction. people also designed an arch-like structure to make the bridges sturdier. these building methods spread far and wide. roman builders build more than 900 bridges.

in today's times, bridges not only make travel and trade easier but also enable people to exchange ideas, cultures, and knowledge. famous bridges of the world such as the london bridge, the golden gate bridge, and the sidney harbour bridge are known for their extraordinary structure, height, weight, or length.

passage 2

natural bridges

bridges are natural or man-made structures that people travel from one place to another in a short amount of time. in meghalaya, a state in northeast india, naturally occurring structures serve as bridges. these are called the living root bridges.

the state of meghalaya experiences heavy rainfall. this makes wooden and bamboo bridges impractical and dangerous. wood and bamboo get damaged when it rains.

in the past, the people of the kahasa tribe in meghalaya faced a lot of difficulties, as the bridges were washed away by heavy rainfall. they felt it was necessary to think of a permanent solution. so, they thought of using roots from trees for making new bridges.

unlike modern bridges, people grew these bridges instead of building them. they used banyan or rubber trees and planted them on riverbanks. unlike most trees, the banyan tree and the rubber tree both have aerial roots that grow above the ground. the roots were then twined to the trunks of beetle nut trees, which grew horizontal to the ground. the trunk of the tree the roots grow in the right direction. the roots were also tied together in such a way that they naturally merged and grew together to provide a sturdier base. the roots continued to grow, and after a few years, natural bridges were formed. once the bridges were formed, people added stones to make a path, so they could walk easily. as this was a naturally occurring process, the bridges took 15 to 20 years to grow. with time, the roots continued to grow and the bridges became stronger.

these living root bridges grow up to 15 to 30 meters long and are strong enough to hold 50 people at a time. in fact, they are stronger than concrete bridges and also last longer. in some cases, living root bridges have lasted for more than 500 years.