Part 1. Definition
In this task, you will be shown an incorrect English sentence. You need to generate a corrected form of the input sentence.
Part 2. Example
The car's wheel are loose.
Answer: The car's wheel is loose.
Explanation: The instance of are is replaced by the word is. This makes the sentence grammatically correct.
Part 3. Exercise
The first clue is that there are rocks near the coast which are considered to be made by Chinese explorers . 
Answer:
The first clue is that there are rocks near the coast which are considered to have been made by Chinese explorers . 