Who first propounded the theory of 'Mantle Plumes'?

Which one of the following is NOT a type of plate boundary?

In the structure of planet Earth, below the mantle, the core is mainly made up of which one of the following?

Which discontinuity is found between the upper mantle and the lower mantle?

Which one of the following is found in the innermost part of the Earth?

Which one of the following is NOT a minor plate?