Echoes occur as sound waves strike a smooth surface and bounces backwards.

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks. 

     People all around the world are more and more associated with social networking, (5) _____ is a useful tool for those in the digital era. Social networking aims at promoting and aiding communication. (6) _____, this type of technology may be doing more (7) _____ than good. It is not only changing how we communicate, but how we associate with each other in everyday life. Sarah Zay, of USA Today, expressed that “With the growth of websites such as Facebook, social networking may be (8) _____ of replacing traditional personal interactions for the future generation”. Traditional interactions will continue to be at risk if we don’t (9) _____ the impacts of our social media. Social networking affects our lives in many ways, including our communication, self-expression, bullying, isolations, companionships, and even our very own sense of humanity.

"Roger, remember that you won't be able to cancel the contract __________.”

These fish live _________ small sea creatures such as the shrimps. 

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions. 

     Robots are useful for exploring and working in space. In particular, many robots have been sent to explore Mars. Such robots have usually looked like a box with wheels. Though these robots are useful, by their very nature they are unreliable, extremely expensive, and they break easily. Also, they cannot do many tasks. Because of these problems, scientists have been developing a new and unusual kind of robot. These new robots move like snakes, so they have been given the name ‘snakebots’. 

     The way a snake is shaped lets it get into very small spaces, like cracks in rocks. It can also push its way below the ground or climb up different kinds of objects like high rocks and trees. Such abilities account for the usefulness of a robot designed like a snake. A snakebot would be able to do these things, too, making it much more effective than regular robots with wheels, which easily get stuck or fall over. Since they can carry tools, snakebots would be able to work in space, as well. They could, for example, help repair the International Space Station. 

     But how can such a robot shape be made? A snakebot is built like a chain made of about thirty parts, or modules. Each module is basically the same in that they all have a small computer and a wheel to aid movement. The large computer in the "head" of the snake makes all of the modules in a snakebot work together. 

     The modular design of the snakebot has many advantages. If one module fails, another can be added easily. Snakebot modules can also carry different kinds of tools, as well as cameras. Since each module is actually a robot in itself, one module can work apart from the rest if necessary. That is, all the modules can separate and move on their own, and then later, reconnect back into a larger robot. Researchers are also trying to develop snakebots made of a special kind of plastic that can change its shape using electricity, almost like animal muscles. Snakebots made with this plastic will be very strong and hard to break. 

     Overall, the snakebot design is much simpler than that of common robots. Thus, snakebots will be much less expensive to build. For example, a robot recently sent to Mars cost over a hundred million dollars, whereas snakebots can cost as little as a few hundred dollars. With their versatility and affordability, snakebots seem to be the wave of the future, at least as far as space robots are concerned. 

I can't figure out Daisy's attitude toward the trip - she is blowing hot and cold about it. First she's all excited, but then she seems reluctant to go. 

The gardener told me that everything __________ by the end of the year.

When Rose arrived home after a day at work, _____________. 

I'll give you some _______ of advice that can help you escape from the trouble.

Jane is talking to Billy about the plan for the field trip next week. 

- Jane: "Are you happy with the plan we have just made?" 

- Billy: “____________” 

We must get to the ________ of the problem and solve it once and for all.

Mark the letter A, B, C, or D to indicate the option that best completes the following exchange.