Question 1
What is an open cover of a set $A$ in a topological space?
Question 2
Which family is an open cover of $[0,1]$ in $\mathbb{R}$ with the usual topology?
Question 3
Must every set in an open cover be open?
Question 4
Can a set have more than one open cover?
Question 5
In the definition of an open cover of $A$, what must be true about the union of the open sets?
