Option B right? Why? What does this mean?

Point B cannot be considered a particle.

Please read the question clearly. If the option is too long, you can perform an abbreviation analysis. After the abbreviation of option b is completed, it becomes :

Players with GPS positioning system. This is easy to understand, if the position of the player displayed on the GPS positioning system can be regarded as a particle, the answer is of course yes, but the meaning of this option is exactly the opposite of what you understand, referring to the player who uses GPS, of course, it cannot be regarded as a particle. If you choose B, it means that you not only did not read the topic clearly, but also did not accurately understand the concept of particles.

Here are the key points that should be taken into account when an object can be considered as a particle (none of these conditions can be met in option B):

First, to treat an object as a particle, it is necessary to look at the nature of the problem under study, and it has nothing to do with the object itself. Therefore, whether an object can be considered as a particle needs to meet one of them:

When the size of the object is extremely small compared to the other distances in the problem under study.

The motion of all parts of an object is the same, and the motion of any point of it can represent the motion of the whole object. [1]

Second, under idealized conditions, the conditions for satisfying are:

1) All points on an object move the same way, which can be regarded as a particle.

2) The size and shape of the object have little impact on the research problem and can be regarded as a particle.

3) A rotating object can also be regarded as a particle as long as its rotation is not studied and in accordance with Article 2.

Third, there are two situations in which a moving object can be regarded as a particle:

1) The shape and size of a moving object are negligible compared to the problem it is studying, such as studying the Earth's revolution around the Sun, and the Earth can be used as a point of mass.

2) For translational objects, one point can be used to represent the motion of the whole object because the motion of each point on the object is the same.

Also, please don't question the answer casually, and think about whether it makes sense when you see the answer.

For each option, just draw an equivalent circuit diagram, as shown in the image below:

The answer is wrong, this question is obviously wrong.

The current will pass through, r1. The current passes through all closed routes.

It's easy to understand when you think of R1 and R2 as 2 bulbs.

Drawing a Venn diagram is obvious:

A intersects B is A, A is a subset of B, and in the diagram, yellow is the complement of A, and the line drawing part is the intersection of the second half of the B option, which is obviously not empty.

is u i = constant constant, at the change of time. However, u i=r increases as the value of the sliding rheostat increases. The total r is getting smaller, so it's wrong.

The ratio of the voltmeter to the ammeter, the voltmeter in the circuit measures the voltage of the ammeter and r, because the internal resistance of the ammeter is very small and negligible, so the voltage can be considered to be the voltage of p.

The ammeter measures the current value in p.

To sum up, u i is actually the resistance value of the resistor p.

The title has already stated that p is a variable resistor, so the invariant statement of option b is definitely wrong.

As can be seen from the figure, the higher the temperature, the higher the solubility of A, the lower the solubility of B, and the temperature from t1 to t2, the temperature increases, the solubility of A increases, and the solubility of B decreases.

Pick D. Emphasized: he has not been to the United States from the beginning of the past until now. So he has never been there...

Has Been emphasizes that he has already been to a certain place, and the person is not necessarily still in that place when he speaks. For example, he had been to England before and now he is back; And has gone emphasizes the action of going somewhere, and the person is no longer here when he speaks.

has gone is ephemeral and means went, while has been is continuous and denotes going.

a, b is in the form has done, and the question needs to be did