Generate a sentence that answers this question: "If a bird is moving through the sky, someone wanting to know the speed would".

Answer: speed is a measure of how fast an object is moving

Generate a sentence that answers this question: "If you wanted to see the source of sunshine you would look at".

Answer: the sun is a source of light called sunlight

Generate a sentence that answers this question: "If a thing reacts in a situation, the most likely reason for the chemical reaction is".

Answer:
adding heat to an object sometimes causes chemical reactions