Past Perfect Tense or Past Simple Tense 1. The teacher ... (check) the tests that we (do). 2. They ... (clean) the room after their aunt... (tell) them about this. 3. I... (give) them some of the candies I ... (buy). 4. My sister ... (live) in Turkey before she ... (move) to Belgium. 5. We ... (be) tired because we ... (work) all day. Past Perfect Tense or Past Simple Tense 1. After Joanna ... (finish) her presentation, we questions. (ask) our 2. Tina and Sophie ... (watch) a film after they ... (wash) clothes. 3. Susan (read) a book after she ... (do) the test. 4. Jimmy ... (to tell) us about the film that he ... (see). 5. Mr Smithson ... (come) his office after a secretary ... (type) letters.
The "acid rain" refers to what scientists call "acid deposition". It is caused by desreuctive airborne acidic pollutants.
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Acis rain was discovered in 1852, when English chemist Robert Agnus invented the term.
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Recently, a more intensive research on the true causes of acid rain has been done so that countries have the information they need to ptevent acid rai and its dangerous effects.
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Air pollution can be found both outdoors and indoors.
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Every year, 14 billion pounds of sewage, sludge and garbage are dumped into the wotld`s oceans.