II.Put the undertined verbs in the sentences in Past Perfect Tense: 1. Ampere determined the difference between the current and the static charges before giving the current direction 2. Men of science formed a lot of theories after Volta produced a source of continuous current. 3. By 1753 Franklin made an important contribution to the science of electricity 4. Galvani observed the experiments with the frogs' legs before Volta began to carry on similar experiments. 5. Volta spent several years before he generated a continuous current.

1. Ampere had determined the difference between the current and the static charges before giving the current direction

2. Men of science formed a lot of theories after Volta had produced a source of continuous current.

3. By 1753 Franklin had made an important contribution to the science of electricity

4. Galvani had observed the experiments with the frogs' legs before Volta began to carry on similar experiments.

5. Volta had spent several years before he generated a continuous current.

He has been talking for 2 years about his trip to Australia.

He has been looking for his book all the morning.

I have been wondering if i couldn't study German a little more.

He has been thinking about his girlfriend all the week.

We have been just talking about you.

I have been writing for you for about thirty minutes.

He has been sitting in that chair all the evening.

We have been traveling though Texas for 4 years.

We have been listening to the radio all the morning.

(?) have/has been waiting for the bus for half an hour.

Объяснение:

В последнем, т.к. вы не написали существительное в начале, я написала два варианта have/has. Если там было he/she/it то выберите has

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