Прочитайте текст. Выберите один из предложенных вариантов ответа. Заполните пропуск (A15).
How much sleep do we really need? This can vary quite a lot between individuals. However, it is widely believed that between
6—8 hours is healthy. What is particularly important is that this sleep happens (A8) ... the right time; that it fits in with our body's natural rhythm. If you suffer (A9) ... sleepiness during (A10) ... day then you are probably not getting enough sleep when you most need it. Typical symptoms of a lack of sleep are (A11) ... low concentration, poor memory and feeling irritable. Getting the right amount of sleep is not only important (A12) ... terms of being able to function properly on a day to day basis but it also has (A13) ... impact on your overall health. Research suggests that people who sleep between 6 to 7 hours per night are likely to live longer than those who sleep less than 6 or more than 8 hours per night. One reason (A14) ... this is because of the effect sleep has (A15) ... our immune system.
Правильный ответ on. To have effect on something — оказывать влияние на что-либо, устойчивое употребление предлога.
Правильный ответ указан под номером 4.