Complete the following alphabet series?
SAB, ?, QCD, PDD, OEF, NFF

Is the father of 'demonstration method'?

Directions : In these questions , a part of the sentence is given in bold . Below are given alternatives to the bold part at (A) , (B) and (C) which may improve the sentence . Choose the correct alternative . In case no improvement is needed you answer is (D ) .

By this time tomorrow, I will reach my home. 

Most people who bother with the matter at all would admit that the English language is in a bad way, but it is generally assumed that we cannot by conscious action do anything about it. Our civilization is decadent and our language-so the argument runs-must inevitably share in the general collapse. It follows that any struggle against the abuse of language is a sentimental archaism, like preferring candles to electric light or hansom cabs to aeroplanes. Underneath this lies the half-conscious belief that language is natural growth and not an instrument which we shape for our own purposes. 
Now it is clear that the decline of a language must ultimately have political and economic causes it is not due simply to the bad influence of this or that individual writer. But an effect can become a cause, reinforcing the original cause and producing the same effect in an intensified form, and so on indefinitely. A man may take to drink because he feels himself to be a failure, and then fail all the more completely because he drinks. It is rather the same thing that is happening to the English language. It becomes ugly and inaccurate because our thoughts are foolish, but the slovenliness of our language makes it easier for us to have foolish thoughts. The point is that the process is reversible. Modern English, especially written English, is full of bad habits which spread by imitation and which can be avoided if one is willing to take the necessary trouble. If one gets rid of these habits, one can think more clearly, and to think clearly is a necessary first step towards political regeneration: so that the fight against bad English is not frivolous and is not the exclusive concern of professional writers. 

Many people believe that nothing can be done about the English language because –

Select the group that has the same relation between the given numbers as the relation between the following group numbers.
(4, 9, 37)