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 teeth.
«lips and lost teeth» – губы и зубы. (tooth – зуб, teeth - зубы) (Единственное и множественное)

TOOTH

20

Statistics show a 26% increase in complaints last year from people with problems from whitening. Many of them used services of unqualified specialists.
«Statistics show a 26% increase in complaints last year» - Статистика показывает, что в прошлом году количество жалоб увеличилось на 26%. (Степени сравнения)

LATE

21

Now we know why a dog’s nose is cold. Scientists have tried / have been trying to solve this mystery for many years. The scientists believe dogs’ noses are cold because dogs sense the temperature of things without touching them.
«Scientists have tried / have been trying to solve this mystery for many years» - Ученые (пытались) и пытаются разгадать эту загадку уже много лет. (Present Perfect / Present Perfect Continuous)

TRY

22

They use their noses to detect temperature, when prey is nearby. Earlier it was believed that dogs’ noses are cold to control their body temperature. Researchers did experiments on dogs, which had to detect the temperature of different objects.
«Earlier it was believed that dogs» - Раньше считалось, что собаки (тогда, в прошлом, считалось) (Past Simple Passive)

BELIEVE

23

Brain activity in the dogs showed that they knew which objects were warmer than others. So dogs adjust their behaviour according to the thermal radiation coming from warm bodies.
«they knew which objects were warmer» - они знали, какие предметы теплее (тогда, в прошлом) (Past Simple – простое прошедшее)

KNOW

24

A researcher said this would change in the future scientists’ ideas on how animals hunt. Many animals may use heat-sensing abilities to hunt.
«A researcher said this would change in the future scientists» - Исследователь сказал, что в будущем это изменится (Reported Speech – согласование времен)

CHANGE