A logic problem that urgently needs to be solved in detail 30

The implication of the stem is clear: stability is a necessary but not sufficient condition for development. In other words: any developing country is necessarily stable, but a stable country is not necessarily developing.

So based on these two sentences, let's take a look at what is wrong with C and D.

Option C "It is impossible for any country to be stable but not develop", this sentence uses a double negation, so the real meaning is that "any country, as long as it is stable, will definitely develop", which is to take "stability" as a sufficient condition for "development". However, in fact, "stability" is only a necessary condition for "development", and a stable country does not necessarily mean that it will be able to achieve development, so the meaning of option C is inconsistent with the question stem and is wrong.

Option d, "Any country, either stable or not developing", puts "stability" and "development" in opposition and allows only one state to exist. The phrase "as long as there is stability and only stability, any country will develop, otherwise it will not develop." ”。

Logically speaking, this sentence actually takes "stability" as a sufficient and necessary condition for "development", but the meaning of the question is very clear: stability is only a necessary condition for development, not a sufficient condition, so option D is also wrong. (As a counter-example, there are countries that are not developing, but at the same time they are stable.)

This would amply prove that the statement of option D that "there can only be one state of stability or non-development" is wrong).

Only stability can lead to the development of any country.

Only. Just. It is said that stability is a necessary condition for development.

And not sufficient conditions.

In other words, stability does not necessarily lead to development, and development does not necessarily mean stability. Therefore, only b is in line with the stem, and nothing else can be derived from the stem.

[Problem Analysis] Correct answer A

In this question, we use the hypothetical counter-proof method, we notice that each person said three sentences, and only the first sentence said by C and D contained a negative, so try to start with the first sentence said by C and D.

There are only two cases for any one sentence, which is either true or false. In the first case, if C's first sentence "I have no brothers and sisters" is true, that is, C does not have any brothers and sisters, she cannot all tell the truth (because the person who always speaks the truth must have more than one brother and sister and more than one child), therefore, the three sentences C says can only be true and false, that is, the second sentence must be false, and the third sentence must be true.

The second case: Suppose that the first sentence C said is false, it means that she has brothers and sisters, since C has a false sentence in what she says and she has brothers and sisters, so what she says can only be true and false, then the second sentence is true, that is, she has sons, so C has more than one brother and sister and more than one child, so what she says should be true, so it contradicts "suppose C's first sentence is false", so the second case is impossible. From this, it can be concluded that what C said can only be the first case, that is, "true or false", and if the third sentence said by C is true, it can be seen that A must have a son.

Using the same method, it can be seen that the three sentences spoken by Ding are the same as C, and they can only be "true, false and true", from which it is concluded that "A is D's brother", that is, A has the sister of D, and A has a son. Therefore, A must always tell the truth. Therefore, a is the correct answer.

Explain logic questions, to give a reason or explanation for a contradictory phenomenon, this kind of problem has two steps: first, find the contradiction, and second, give an explanation for the contradiction.

First of all, the contradiction in the original text can be in catalytic converters.

Reduce Nitrogen dioxide emissions, and this catalytic converters are required to be installed in new cars, but the proportion of new cars in Donia's Capital City is high, but why the reduction of nitrogen dioxide emissions is not obvious, secondly, to give an explanation for this contradiction, there are many new cars, that is, catalytic There are many converters, but there are many catalytic converters but they can't reduce the emission of nitrogen dioxide, that many are useless, and they are ineffective, this is one aspect that can be explained, the original text says that catalytic converters can reduce nitrogen dioxide, we don't want to object to this fact, we just want to see if the occurrence of this fact requires conditions, If a condition is needed for this fact to be true, then the contradiction can be explained, such as option e.