Which one of the following conditions correctly describes the manner of determining the sex?

$Fe$ is made passive by

Two slabs $A$ and $B$ of equal surface area are placed one over the other such that their surfaces are completely in contact. The thickness of slab $A$ is twice that of $B$. The coefficient of thermal conductivity of slab $A$ is twice that of $B$. The first surface of slab $A$ is maintained at $100^{\circ} C$,while the second surface of slab $B$ is maintained at $25^{\circ} C$. The temperature at the contact of their surfaces is (in $^{\circ} C$)

The set of solutions of the equation $(\sqrt{3}-1) \sin \theta+(\sqrt{3}+1) \cos \theta=2$ is

Let $A$ and $B$ be two sets. Then $(A \cup B)' \cup (A' \cap B)$ is equal to:

The angles of a triangle are in the ratio $3: 5: 10$. Then the ratio of the smallest side to the greatest side is: