Mathematics for IGCSE & O level - Sets (Section 2 - No. 23)
What does it mean for a set 'A' to be a subset of set 'B'?
All elements of A are also elements of B
All elements of B are also elements of A
A and B have no common elements
A contains all elements of the universal set
Explicação
A subset contains elements that are all also members of another set.