Расположите этапы мышечного сокращения в правильной последовательности.
1-ионы кальция связываются с тропонином на актиновых филаментах.
2-актиновые филаменты скользят относительно друг друга.
3-импульс
двигательного нерва вызывает высвобождение ацетилохолина,который
вызывает открытие ионных каналов в мембране мышечной клетки и развитие
потенциала действия.
4-из саркоплазматического ретикулума в саркоплазму высвобождаются ионы кальция.
5-миозиновая головка наклоняется и тянет актиновый филамент.
6-тропонин приподнимает тропомиозин,освобождая активные участки актина.
7-ионы кальция перекачиваются в саркоплазматический ретикулум.
8-мышечное сокращение заканчивается.

. Прочтите текст "Acid Rains " и выберите единственно правильный ответ.
ACID RAINS
Every year more and more plants and animals disappear never to be seen
again. Strangely, it is the most intelligent but most thoughtless animal that is
causing most of the problems — man. Nature is very carefully balanced and if
this balance is disturbed, animals can disappear alarmingly fast. Every day,
thousands of species of animals draw closer to extinction. There are countless
number of species which may become extinct before they are even discovered.
In many lakes the fish are dying. Fishermen are worried because every year there
are fewer fish and some lakes have no fish at all. Scientists are beginning to get
worried too. What is killing the fish?
The problem is acid rain. Acid rain is a kind of air pollution. It is caused by
factories that burn coal or oil or gas. These factories send smoke high into the
air. The wind often carries the smoke far from the factories. Some of the
harmful substances in the smoke may come down with the rain hundreds of
miles away.
The rain in many places isn't natural and clean any more. It's full of acid
chemicals. When it falls in lakes, it changes them too. The lakes become more
acidic. Acid water is like vinegar or lemon juice. It hurts when it gets in your
eyes. It also kills the plants and animals that usually live in lake water. That is
why the fish are dying in lakes.
But dead fish may be just the beginning of the problem. Scientists are finding
other effects of acid rain. In some large areas trees are dying. Not just one tree
here and there, but whole forests. At first scientists couldn't understand why.
There were no bugs or diseases in these trees. The weather was not dry. But
now they think that the rain was the cause. Acid rain is making the earth more
acidic in these areas. Some kinds of trees cannot live in the soil that is very
acidic.
Now scientists are also beginning to study the effects of acid rain on larger
animals. For example, they believe that some deer in Poland are less healthy
because of acid rain. If deer are hurt by the rain, what about people? This is the
question many people are beginning to ask. No one knows the answer yet. But
it is an important question for us all.

Вопросы к тексту:
1. This passage is about
(A) fishing.
(B) acid rain.
(C) air pollution.
(D) destructive human activity.
2. Every year thousands of species of animals
(A) are hunted for their meat and skins.
(B) migrate to other places.
(C) starve to death.
(D) die out.
3. Acid rain is caused by
(A) natural gas.
(B) the ozone layer depletion.
(C) acidic lake water.
(D) emissions of industrial enterprises.
4. Which of the following is true?
(A) Dead fish in lakes is the only problem caused by acid rains.
(B) Scientists are sure that acid rains are not harmful for mankind.
(C) If we don't make an attempt to stop acid rains we may never see
some animals again.
(D) There's no reason to worry about several trees that died of some
unknown disease.
5. What was not mentioned in the text?
(A) Acid rain is capable of dissolving some rocks and stones.
(B) Fish are unable to live in the water containing acidic chemicals.
(C) Coal, oil or gas form dangerous combinations after being burnt.
(D) Scientists reckon that if some larger animals can be affected by acid rains,
people may be in great danger.
6. Factory smoke
(A) stays over the factories.
(B) is usually clean now.
(C) turns into air.
(D) can travel hundreds of miles.
7. Scientists think acid rain
(A) is killing people.
(B) helps kill bugs.
(C) fertilizes the soil.
(D) is killing trees.