Problem: How often are American presidential elections held?
Answer: every four years

Problem: What is the musical term for one or more vocalists performing without an accompaniment?
Answer: cappella

Problem: 21 October, 1833 saw the birth of Swedish scientist Alfred Nobel, who amassed his considerable fortune following his invention of what?
Answer: dynamite

Problem: Which Armenian composer wrote the ballets Gayaneh and Spartacus?
Answer:
khachaturian