Draw inferences for the following pairs of statements
Some books are hooks.
Some hooks are not books.

Explanation

Here, the two sentences do not have the same subject and predicate. Books is the subject of the first sentence and the preidcated of the second while hooks is the predicate of the first sentence and the subject of the second. Hence the stentencs do not apear to be complementary. But if we convert the first sentence from . some books are hooks to Some hooks are books the two sentences have the same subject and predicate now, and being an .I and O. pair they are complemnetary.
With all these forgoning discussions in mind, let us come back to our original questions, which is. when is the answer choice .either of the two follows. correct ?
You must be aware that usually there are the following five choices.
(i) Only A follows (ii) Only B follows
(iii) Both A and B follow
(iv) None of them follows
(v) Either A or B follows
Now, when you read a question, you first read the statements and then the answer choices. You take the first choice A and chek whether it is correct or not. then you go to the second choice, B and check it. suppose none of the two choices come out to be correct . What should you do next ? Do you then opt for the choice None of them follows.. ? No, this is not the correct , you should check whether the choice ..Either of the two follows " is also incorrect, then you should move on the last choice, viz. None of the them follows. this finally, brings us to the answer of our original question :
The choice "Either of the two follows" should be chosen if
a. none of the given two choices are found to be correct, and
b. the two choices form a complementary pair.
The rule is explained by way of the following examples: