In a , a central authority determines who buys goods and services. in a _
determines who buys these products,
economy, price
planned, market
market, planned

In a planned economy, a central authority determines who buys goods and services. In a market economy determines who buys these products.

Explanation:

In a planned economy, the market has a secondary role for the allocation of resources.

Market economy is understood as the organization and allocation of the production and consumption of goods and services arising from the interplay between supply and demand.

first one is the correct answer

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.