Test: Reading Comprehension- 3 - Bank Exams MCQ

As mentioned in the passage, "A slip of the tongue, the use of an unusual word, or of an ambiguous word, and so on, may create an enemy where we had hoped to win a friend.", an 'ambiguous word' may create an enemy instead of winning a friend.
Hence the best way to win a friend is by not using an ambiguous word, or 'to avoid ambiguity in speech'.

The passage tells us that we should handle the gift of speech carefully. While talking to another person we should use the speech he is most familiar with. In the case of an uneducated person also we should use the vocabulary he is most familiar with because "the ordinary speech of an educated man may strike an uneducated listener as pompous."

The sentence in the passage is "A 'slip of the tongue', the use of unusual word, or of an ambiguous word, and so on, may create an enemy where we had hoped to win a friend. ".
So, the term 'slip of tongue' is came with such things having similar meaning of lack of proper thought.

"Speech is a great blessing but 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." An example being: "A slip of the tongue...may create an enemy where we had hoped to win a friend."
Option A also mentions the same: speech can be a curse because it can 'make our attitude completely misunderstood'.