TASK DEFINITION: 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.
PROBLEM: Question: What occurs when a substance reacts quickly with oxygen? Answer: combustion reaction

SOLUTION: Combustion reaction occurs when a substance reacts quickly with oxygen.

PROBLEM: Question: The complement system is a series of proteins constitutively found in the what? Answer: blood plasma

SOLUTION: The complement system is a series of proteins constitutively found in the blood plasma.

PROBLEM: Question: Blood enters the heart in what valve? Answer: atria

SOLUTION:
Blood enters the heart in atria valve.