You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.
Q: Paragraph- Sent 1: What if two children push a swing at the same time?
Sent 2: Would the swing go higher?
Sent 3: Yes, together their force would be more.
Sent 4: It is common for forces to be combined.
Sent 5: Most objects on Earth have at least two forces acting on them.
Sent 6: Do you know what one of them is?
Sent 7: Of course, that force is gravity.
Sent 8: How many forces do you have on you right now?
Sent 9: Gravity pulls you down toward the center of Earth.
Sent 10: Your legs exert a downward force.
Sent 11: They hold you up against the pull of gravity.
Sent 12: Consider the example in Figure 1.3.
Sent 13: A book is resting on a table.
Sent 14: Gravity pulls the book downward.
Sent 15: It has a force of 20 newtons.
Sent 16: At the same time, the table pushes the book upward.
Sent 17: Its force is also 20 newtons.
Sent 18: The table opposes the pull of gravity. 
Question: Why would a swing go higher when two children push it at the same time? (A) There is more gravity on the swing (B) Together, their force would be more (C) There is more force acting on the swing.
A: 
B, C.