3) Is this sentence correct:
There are many reasons for extinction : pollution, hunting, fishing and deforestation .
However, I would choose Number 2. "There are several reasons for this. One [reason] is that man often hunts and fishes too efficiently nowadays". (You are talking about �reasons �, not �things �).
I have no problem with Sentence 3, except possibly, the addition of some words:
" There are many reasons for the extinction of plants/animals: pollution, hunting, fishing and deforestation". In British English, the preposition �for � is perfectly acceptable.
3)What is the difference between these verbs : circle & encircle ??
Can we use them Interchangeably?
Oxford Dictionary of English.
�Circle�
1. �Circle� - verb, with object. �Move all the way around�; �Fly around repeatedly�; Example: "We circled round the island".
2. �Circle� - verb, with object. �Form a ring around�; Example: "The abbey was circled by a huge wall".
3. �Circle� - verb, with object. �Draw a line around�; Example: "Circle the correct answers".
�Encircle�
1. �Encircle� - verb, with object. �Form a circle around�; �Surround�; Example: "The town is encircled by fortified walls".
Can we use them Interchangeably?
Looking at example 2 for �Circle� and example 1 for �Encircle�:
"Yes!" (But ONLY with these meanings, "Form a ring around" and "Form a circle around". Not with the others! A �ring� and a �circle� are very similar.)
I hope that this helps you.
Les