Given a scientific passage and an answer, generate a question for the given answer.

Ex Input:
Passage: Hinge Joint. The knee joint is a hinge joint. Like a door hinge, a hinge joint allows backward and forward movement. Answer: hinge joint

Ex Output:
What type of joint is the knee joint?

Ex Input:
Passage: The heat that is either absorbed or released is measured in joules. The mass is measured in grams. The change in temperature is given by , where is the final temperature and is the initial temperature. Answer: joules

Ex Output:
In what unit is heat measured in?

Ex Input:
Passage: [PCl 3][Cl 2] (0.135)(0.135) = = 0.021 0.87 [PCl 5] The equilibrium constant calculated from the equilibrium concentrations is equal to the value of Kc given in the problem (when rounded to the proper number of significant figures). Thus, the calculated equilibrium concentrations check. Kc =. Answer: in nature

Ex Output:
Because of their reactivity, we do not find most representative metals as free elements where?