Final answer:
Magnesium is the member of the alkaline earth metals that is used to make both fireworks and medicines, making it the correct answer to the student's question.
Step-by-step explanation:
The student's question involves identifying which of the listed elements is a member of the alkaline earth metals used to make both fireworks and medicines.
The alkaline earth metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Among these, magnesium is well-known for its use in fireworks due to its bright-burning properties, as well as its applications in medicines. For example, it is used in antacids to neutralize excess stomach acid. On the other hand, lithium is a member of the alkali metals, specifically used in batteries and certain psychiatric medications, but not typically associated with fireworks. Therefore, the correct answer is magnesium (3).