In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
All this suggests the intimate relations which exist between history, politics, and sociology. The ____________ thing, however, is not the identities but the distinctions.For, however much the _____________ disciplines may, in practice, overlap, it is necessary ________ the sake of clear thinking to have their limits defined. As far _______sociology and history are concerned the differences may be summed up in a word. __________ history and sociology are concerned with the life of man as man.
it is necessary ________ the sake of clear thinking