Question: it has been suggested that the idea of complementarity came from outside physics, some arguing that the roots of the idea came from the discussions with his father, christiansen and the philosopher hoffding when he was still at school.
Answer: --> It has been suggested that the idea of complementarity came from outside physics, some arguing that the roots of the idea came from the discussions with his father, Christiansen and the philosopher Hoffding when he was still at school.

Question: a hectic period began.
Answer: --> A hectic period began.

Question: easy spreading of sand, salt and grit
Answer:
--> Easy spreading of sand, salt and grit