Why is it difficult to test the efficacy of biofeedback using experimental techniques?
a.
it is difficult to devise a control treatment that replicates biofeedback.
b.
biofeedback cannot be subjected to testing because it is pseudoscience.
c.
the principles of biofeedback are not entirely understood.
d.
biofeedback is not concerned with any scientific subject

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.