Вставить артикль, где необходимо: 1. many years ago _ rivers began to speak against _ sea. _ rivers came to _ sea and said "we bring _ sweet water to you, and you make it salt. _ people can't drink this _ water. why do you do that? " "if you do not like _ salt water", answered _ sea, "run to _ some other place". 2. once _ two friends were in _ thick wood, when they met _ bear. one of _ men was very much frightened by _ bear. he ran to _ high tree and got up into it. _ other man understood that he could not stand up against _ big bear. he lay down on _ grass. "_ bear will think that i am dead", he said to _ himself. _ man thought that _ bears do not atack _ dead people. _ bear came up to _ man on grass, sniffed at _ his nose and went away. _ other man got down from _ tree. "what did _ bear say in _ your ear? " he asked him. "he told me", was _ answer, "not to go into _ woods with _ bad friend who will not help you in _ danger." 3. _ man built _ house for _ himself. _ house was nice, but very small. he invited _ friends to see it. _ friends came and looked at _ house. every man said something bad about it. "_ front of _ house is not nice." "_ windows are very small." "_ roof is not good, _ rain will come in." "_ rooms are not large enough for _ man." _ man listened and answered, "you may be right. _ house is small, but it is big enough for _ me and i have no _ good friends to invite to _ my house."

1.Many years ago a rivers began to speak against a sea. the rivers came to the sea and said "We bring  sweet water to you, and you make it salt.  people can't drink this  water. Why do you do that?" "If you do not like salt water", answered the sea, "run to some other place.
2. Once two friends were in a thick wood, when they met a bear. One of the men was very much frightened by the bear. He ran to a high tree and got up into it. The other man understood that he could not stand up against the big bear. He lay down on grass. "the bear will think that I am dead", he said to himself.  The  man thought that bears do not atack  dead people. The bear came up to the man on grass, sniffed at his nose and went away. The other man got down from the tree. "What did the bear say in your ear?" he asked him. "He told me", was  answer, "not to go into woods with bad friend who will not help you in danger."
3. A man built a house for himself. The house was nice, but very small. He invited friends to see it. The friends came and looked at the house. Every man said something bad about it. " a front of the house is not nice." " windows are very small." "a roof is not good, rain will come in." " rooms are not large enough for man." The man listened and answered, "You may be right. The house is small, but it is big enough for me and I have no the good friends to invite to my house."
a/an неопределенный, то есть используется, когда предмет впервые упоминается в тексте. в дальнейшем говоря об этом предмет нужно использовать the определенный артикль.
a/an не используются с неисчисляемыми и перед существительными во множественном числе.