When should you use a composite primary key?

Question $17$ options:

a$)$

As identifiers of weak entities, in which the strong entity has a strong identifying relationship with the parent entity

b$)$

As identifiers of composite entities, in which each primary key combination is allowed only once in the M:N relationship

c$)$

As identifiers of strong entities, in which the weak entity has a strong identifying relationship with the parent entity

d$)$

As identifiers of composite entities, in which each primary key combination is allowed only once in the $1$:M relationship