It is false that no jailhouse informants are people who can be trusted. therefore, some jailhouse informants are not people who can be trusted.

The correct answer is invalid.

The statement says: It is false that no jailhouse informants are people who can be trusted. Therefore, some jailhouse informants are not people who can be trusted.

So to solve this we used the Traditional Square of Opposition to resolve the inference and see if it's valid or not. Let's remember that the Traditional Square of Opposition helps us to show the opposition lines or its arrangement to see the logically necessary relations between the categorical propositions that are the Contradictory, opposite truth value. Contrary, one is false. Sub contrary, one is true. And Sub alternation, when falsity flows upwards and truth flows downwards.

two jet streams that directly affect the formation of weather in the continental part are a polar jet and a subtropical jet. they are responsible for the transportation of weather systems, which directly affect people. the polar front is the boundary between cold air from the north pole and warmer equatorial air. both the polar jet and the subtropical jet blow from the west to the east, and follow the boundary between cold and warm air.

the strongest jet streams are polar jets, while subtropical jets are somewhat weaker.

the right answer is c. the polar jet stream is generaly stronger than the subtropical jet stream.