TASK DEFINITION: You are given a question, its answer, and a sentence that supports the question, i.e., the answer to the question is inferable from the sentence. In this task, you need to paraphrase the given sentence so that the paraphrased sentence still supports the question i.e. you can still infer the answer to the question from the paraphrased sentence. Do not write a paraphrase with a minor change in the given sentence e.g. replacing the word "one" with "a". Instead, try to write a paraphrase that contains new words, i.e. the words that are not present in the input sentence.
PROBLEM: Question: The concentration of the hydrogen ion in a solution can be calculated when what is known? 
Answer: ph. 
Sentence: The concentration of the hydrogen ion in a solution can be calculated when the ph is known.

SOLUTION: If the ph is known then the concentration of the hyrdorgen ion in a solution can be calculated.

PROBLEM: Question: Which trait can children inherit from their parents? 
Answer: brown eyes. 
Sentence: Children can inherit brown eyes from their parents.

SOLUTION: A parent can pass brown eyes to a child.

PROBLEM: Question: Elements on the Periodic Table of the Elements are classified into categories such as? 
Answer: metals and nonmetals. 
Sentence: Elements on the periodic table of the elements are classified into categories such as metals and nonmetals.

SOLUTION:
Categories of the periodic table of elements include categories like metals and nonmetals.