Answer:
Plate tectonics is a major factor that explains how heat from the core reaches the surface.
Answer: Option 'b' is correct.
Explanation:
Workers originally formed unions with the help of which they can protect themselves from intolerable work conditions and unfair treatment such as low wage, late working hours, exploitation, unhygienic working condition, unsafe atmosphere etc.
And many workers had problems with their leaders or managers due to membership in unions.
Hence, Option 'b' is correct.
