Many ________ trees must be planted every year.

A. thousand  B. thousand of  C. thousands of  D. thousand

阅读下面题目，判断正误， 请在不改变句子意思的前提下， 改正其中的错误部分。

(1) Zhou Gang is a worker at Yulin in Shanxi. He

(2) works on the Great Green wall with many other peoples.

(3) We visited him at his workplace between the young trees

(4) and told him about his work. "Many thousands of trees

(5) must be plant every year," he said. "The more, the better.

(6) This year alone, we've already planted ten thousand of trees.

(7) You see all that small trees over there on the hills

(8) That was sand five years later. Now it's a young forest! In a few

(9) years' time, those mountains will be covered with trees,

(10) too!" He pointed the high mountains away.