An exhibition is an event or display of artwork, like paintings, for public viewing and a concert is an event or performance where music, such as a symphony, is presented. Both relationships involve an event where a particular type of art or performance (painting or symphony) is showcased.

Orthopedics is the branch of medicine that deals with bones, including their structure, function, and treatment and a nephrologist is a doctor who specializes in the kidney and its functions. The analogy is between a medical specialty and the body part it specifically focuses on. Orthopedics focuses on bones, and nephrology focuses on kidneys.

"DOUBT : FAITH" suggests an opposition or contrast between doubt and faith, where doubt is the lack or absence of faith. Similarly, in option B, "Apostate : State," an apostate is someone who renounces or abandons their religion or belief system, which can be seen as a contrast to someone who remains loyal to the state. Both analogies represent a shift or abandonment from one state (faith, belief) to its opposite or absence (doubt, apostasy).

A "convict" is someone who has been found guilty of a crime and is subjected to "imprisonment" as a consequence. Similarly, "exile" refers to someone being banished or expelled from their country, which is a form of punishment or consequence. Both pairs represent a person and the corresponding punishment or consequence.

A subpoena is a legal order that requires a witness to testify in court and Espionage is the act of spying, often carried out by someone working undercover. Both relation props involve a specific action or legal function and a person in a specific role. A subpoena requires a witness, just as espionage requires someone working undercover.

Saliva contains enzymes that help with digestion. Similarly, milk contains nutrients that nourish the body. Both are substances that contain important components for a specific function.

A libretto is the text or script for an opera, just as a score is the written music for a symphony. Both describe the essential written component of their respective musical forms.

"Saccharin" is an artificial substitute for "sugar." Similarly, "margarine" is an artificial substitute for "butter." Both pairs involve a natural substance and its synthetic or substitute counterpart.

Sunlight can energize or revitalize living organisms, just as antibodies can protect the body from illness. Both involve a relationship of one thing providing energy or protection to another.

A slur is a distortion or unclear articulation in speech, just as a smudge is a distortion or unclear mark in writing. Both represent something that mars or interferes with clarity.