Hannah just finished building a house of cards that stands four stories high. She is worried that it will fall down.

Question

Which of the following statements is definitely true?
A.
If Hannah adds another card to the house of cards, then it will fall down.
B.
A house of cards is too fragile and must fall down eventually.
C.
If no unbalanced force acts upon the house of cards, then it will remain standing forever.
D.
As long as nobody touches the house of cards, it will remain standing.

Answer 1

C. If no unbalanced force acts upon the house of cards, then it will remain standing forever.