Which statement about AHf is true?

A)It is zero for any compound in its standard state.
B)It is positive when the bonds of the product store more energy than those of the reactants.
C)It is negative when a compound forms from elements in their standard states.
D)It is zero for any element that is in the liquid state.

How does the digestive system interact with the circulatory system? a. messages sent as electrical impulses from the digestive system are transported throughout the body by the circulatory system. b. nutrients taken in and broken down by the digestive system are carried to various parts of the body by the circulatory system. c. nutrients and gases are absorbed by organs in the circulatory system. then, they are transported to all parts of the body by organs in the digestive system. d. oxygen and carbon dioxide are exchanged by organs in the digestive system, and the gases are carried to the rest of the body by the circulatory system.