One type of cold remedy is an effervescent tablet that breaks down in water. When the tablet is placed in water, it forms gas bubbles. In this example, the formation of a gas A is a physical property.
B occurs when adding water to acid.
Cis a sign of a chemical change.
D occurs when the water boils.

is a sign of a chemical change

Explanation:

The tablet reacts with the water to form carbon dioxide

dopamine..

"it was found that some people who were taking the drug l-dopa to raise their levels of dopamine were developing schizophrenic-like symptoms supporting research a strength of the dopamine hypothesis is that there are many studies which have shown support for the neurochemical explanation."