Why was the idea of plate tectonics difficult for many scientists to accept for many years after it was first introduced?

question 10 options:

it was highly biased

there was no explanation yet for how it was happening

I think the correct answer from the choices listed above is the second option. The  idea of plate tectonics was difficult for many scientists to accept for many years after it was first introduced because there was no explanation yet for how it was happening. It was only to the recent times that these were proven. 

B) raising the temperature and reducing the volume of the gas.|-/