In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

[EX Q]: Question: What do craters and rifts become when the fill with water? Answer: lakes
[EX A]: Craters and rifts become lakes when they fill with water.

[EX Q]: Question: When different types of tissues work together to perform a unique function, what do they form? Answer: organ
[EX A]: When different types of tissues work together to perform a unique function, they form organ.

[EX Q]: Question: What process, which results because of great pressure at the center of a star, causes stars to shine? Answer: nuclear fusion
[EX A]:
Nuclear fusion, which results because of great pressure at the center of a star, causes stars to shine.