Which body systems help to exchange oxygen and carbon dioxide? A. respiratory and digestive
B. circulatory and digestive
C. respiratory and circulatory
D. digestive and excretory

Which type of substance ionizes partially and gives off hydrogen ions when dissolved in water? a. strong acid b. strong base c. weak acid d. weak base

Two metal blocks that have slightly different temperatures are placed next to one another. after five minutes, they both have lower but equal temperatures. according to the law of conservation of energy, what  most likelyhappened? energy was created inside the blocks.energy was destroyed inside the blocks.energy was absorbed into the blocks from outside the system.energy was transferred from the warmer block to the cooler block.

Which statement best describes isomers? a. isomers are alcohols that have the same functional group. b. isomers have at least one carbon-carbon double bond. c. isomers have the same molecular formula but different structural properties.