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

  Scientists have developed a new bionic computer chip that can be mated with human cells to combat disease. The tiny device, smaller and thinner than a strand of hair, combines a healthy human cell with an electronic circuitry chip. Doctors can control the activity of the cell by controlling the chip with a computer.

  It has long been established that cell members become permeable when exposed to electrical impulses. Researchers have conducted genetic research for years with a trial-and-error process of bombarding cells with electricity in an attempt to introduce foreign substances such as new drug treatments or genetic material. They were unable to apply a particular level of voltage for a particular purpose. With the new invention, the computer sends electrical impulses to the chip, which triggers the physicians to open a cell’s pores with control.

          Researchers hope that eventually they will be able to develop more advanced chips whereby they can choose a particular voltage to activate particular tissues, whether they be muscle, bone, brain, or others. They believe that they will be able to implant multiple chips into a person to deal with one problem or more than one problem.

The word they in the first sentences of the third paragraph refers to      _________.

A. chips

B. tissues

C. voltages

D. researchers

Tìm ƯCLN rồi tìm ƯC của các số sau:

a) 54 và 48

b) 45 và 60

c) 48, 72, 90

d) 56, 84, 140

A. 12, 44; 56         

B. 15, 35, 55

C. 75, 94, 12

D. 20, 100, 50

A. 0

B. 2

C. 5

D.  Cả A và C

I’m sorry, but I’ve got ________ much work to do to come to the beach today.

A. too

B. such

C. enough

D. so

Cho 11,6g anđehit propionic tác dụng vừa đủ với V(l) H₂(đktc) có Ni làm xúc tác. V có giá trị là

A. 6,72                     

B. 8,96                       

C.4,48         

D.11,2

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 38 to 42.

HISTORY OF THE HELICOPTER

Although first flight generally attributed to a fixed-wing aircraft, the helicopter actually represents the first style of flight envisioned by humans. The ancient Chinese developed a toy that rose upward when spun rapidly. As early as the mid-sixteenth century, the great Italian inventor Leonardo da Vinci had drawn a prototype for the machine that we now know as the helicopter.

Early in the twentieth century, a great deal of experimentation and revision was taking place with regard to helicopter flight. The well-known phrase “two steps forward and one step back” provided an apt descriptor for early flight development. Uneven lift, known as dissymmetry, caused the early helicopters to flip over and confounded the inventors until the creation of the swash-plate; this allowed the rotor blade angles to be changed so that lift would be equal on each side of the shaft.

On November 13, 1907, the French pioneer Paul Cornu made history by lifting a twin-rotor helicopter into the air for a few seconds without ground assistance. Several models followed without significance until in 1924 when another French pioneer, Etienne Oehmichen, became the first to fly a helicopter for one kilometer. It was a historic flight of 7 minutes and 40 seconds. By 1936, solutions have been found to many of the problems with helicopter flight.

With the introduction of the German Focke-Wulf Fw 61, the first practical helicopter became a reality.

What is the topic of the passage?

A. Which aircraft was the first to fly

B. Aircraft design in the 20th century

C. The development of the helicopter

D. The invention of the swash plate