Examine the following statements: 1) None but the rich can afford air-travel. 2) Some of those who travel by air become sick. 3) Some of those who become sick require treatment. Which one of the following conclusions can be drawn from the above statements?

The question asks for a conclusion that can be drawn from the given statements. Let's analyze each statement and option:

Statements:

1. None but the rich can afford air-travel.
2. Some of those who travel by air become sick.
3. Some of those who become sick require treatment.

Analysis of Statement 1: "None but the rich can afford air-travel." This is a critical statement. It means that being rich is a necessary condition for affording air-travel. If someone can afford air-travel, they must be rich. Conversely, if someone is not rich, they cannot afford air-travel. This can be rephrased as: "Only the rich can afford air-travel," or "If a person travels by air, then that person is rich."

Analysis of Statement 2: "Some of those who travel by air become sick." This statement tells us that a subset of air travelers become sick. It does not apply to all air travelers.

Analysis of Statement 3: "Some of those who become sick require treatment." This statement tells us that a subset of sick people require treatment. It does not apply to all sick people.

Now let's evaluate the options:

A) All the rich persons travel by air

• Statement 1 says that only the rich can afford air-travel, not that all rich persons do travel by air. A rich person might choose not to travel by air, or might not be interested. So, this conclusion is not supported.

B) Those who travel by air become sick

• Statement 2 says "Some of those who travel by air become sick." "Some" means "not all." Therefore, we cannot conclude that all those who travel by air become sick. This conclusion is too strong.

C) All the rich persons become sick

• We know that rich persons can travel by air (Statement 1) and some who travel by air become sick (Statement 2). However, this does not mean all rich persons become sick. Many rich persons might not travel by air, or if they do, they might not get sick. This conclusion is not supported.

D) All those who travel by air are rich.

• This conclusion directly follows from Statement 1: "None but the rich can afford air-travel." If someone travels by air, it implies they could afford it. And if they could afford it, then according to Statement 1, they must be rich. This is a direct logical inference.

Therefore, the only conclusion that can be drawn from the given statements is D.