Explanation

Speech is a great blessing but it can it can also be a great curse; for while it helps us to make our intentions and desires known to our fellows, it can also, if we use it carelessly, make our attitude completely misunderstood. A slip of the tongue, the use of an unusual word, of an an ambiguous word, and so on, may create an enemy where we had hoped to win a friend. Again different classes of people use different vocabularies and the ordinary speech of an educated man may strike an uneducated listener as pompous. Unwillingly we may use a word that hears a different meaning to our listener from what it does to men of our own class. Thus speech is not a gift to use lightly without thought, but one which demand careful handling. Only a fool will express himself alike to all kinds and conditions of men. 

Q. The best way to win a friend is to avoid:

Ans: Ambiguity in speech 

Q: While talking to an uneducated, we should use:

Ans: His vocabulary 

Q: If one used the same style of the language with everyone, one would sound: 

Ans:  Foolish 

Q. A 'Slip of Tongue' means something said:

Ans: Unintentionally 

Q. Speech can be curse, because it can:

 Ans: Create misunderstanding