19

The perfect smile has created a multi-billion-dollar industry, but not all is shiny in this business. Dentists say that illegal whitening is putting people at risk of health problems, including burnt gums, lips and lost ………………… .

TOOTH

20

Statistics show a 26% increase in complaints ………………… year from people with problems from whitening. Many of them used services of unqualified specialists.

LATE

21

Now we know why a dog’s nose is cold. Scientists ………………… to solve this mystery for many years. The scientists believe dogs’ noses are cold because dogs sense the temperature of things without touching them.

TRY

22

They use their noses to detect temperature, when prey is nearby. Earlier it ………………… that dogs’ noses are cold to control their body temperature. Researchers did experiments on dogs, which had to detect the temperature of different objects.

BELIEVE

23

Brain activity in the dogs showed that they ………………… which objects were warmer than others. So dogs adjust their behaviour according to the thermal radiation coming from warm bodies.

KNOW

24

A researcher said this ………………… in the future scientists’ ideas on how animals hunt. Many animals may use heat-sensing abilities to hunt.

CHANGE