[填空题]
The passage contains TEN errors. Each indicated lie contains a maximum of ONE error. In each case, only ONE word is involved. You should proofread the passage and correct it in the following way."
For a {{U}}wrong{{/U}} word, underline the wrong word and write the correct one in the blank provided
at the end of the line.
For a {{U}}missing{{/U}} word, mark the position of the missing word with a "∧" sign and write the word
you believe to be missing in the blank provided at the end of the line.
For an {{U}}unnecessary{{/U}} word, cross the unnecessary word with a slash "/" and put the word in the blank
provided at the end of the line.

The world’s population continues to grow. There now are about 4 billion of us on
earth. That could reach 6 billion by the end of the century