What is the time gap in occurrence of two successive tides at a given place on the ocean surface?

The Sun is seen little before it rises and for a short while after it sets. This is because of

Which one of the following can be said to be essentially related to 'Polar Front Theory'?

Brahmaputra and Indus rivers are antecedent rivers. Which one of the following may be the true definition of an antecedent drainage?