Detailed Instructions: You are given a question or fill-in-the-blank question, two answer options (Option1 and Option2) and an Explanation. Your task is to find the correct answer (return the string of the correct option, not option1/2) for the given question from the given options and using explanation.
Q: Question: If planet W and planet X have a combined mass that is half that of the combined mass of planet Y and planet Z, the gravitational force between planets Y and Z will be _____ that of W and X. 
 Option1: less than 
 Option2: greater than 
 Explanation: The greater the mass of the objects, the stronger the gravitational force of attraction between them.
A:
greater than