Question

which of the following best completes the analogy?
carbon dioxide/gas/carbonic acid
carbonic acid/dissolved ion/carbon dioxide
carbon dioxide/liquid/carbonic acid
carbonic acid/dissolved ion/carbon dioxide

Explanation:

Carbon dioxide is a gas and when it dissolves in water, it forms carbonic acid (a liquid - like solution in this context). The relationship is gas - liquid in terms of the substance and its state/derived form.

Answer:

A. Carbon dioxide/Gas/Carbonic acid