A neutrino is a type of fundamental particle with no electric charge, little or no mass, and one-half unit of spin. It belongs to the family of particles called leptons,which are not subject to the strong nuclear force. Neutrinos are the most freely moving subatomic particles because they react with matter only through a force known as the weak interactin. Neutrinos do not cause molecules to gain or lose electrons, because they are not electrically charged.Only 1 in 10 billion, traveling through matter a distance equa; to the Earth`s diameter, reacts with another substance. There are three types of meutrino, known to scientist as the electron, muon, and tau.
The electron-neutrino was proposed in the early part of the century by the Australian physicist Wolfgang Pauli to explain the apparent loss of energy in the process of radioactive decay. The Italian-born physicist Enrico Fermi further elaborated the proposal and gave the particle its name. Electron-neutrinos were first experimentally observed in the 1950`s. An electron-neutrino is emitted along with a positron in positive radioactive decay, while an electron-antineutrino is released with an electron in negative radioactive decay.
Another type of neutrino, produced with different types of atomic particles decay, was conclusively shown to be so dissimilar to electron-neutrinos and electron-antoneutrinos that is was classified as a completely different species: the muon-neutrino. These new forms of neutrino are as free moving as the othe neutrino. However, muon-neutrinos have different characteristics when they react with other particles. In the mid-1970`s, particle physicist discovered yet another variety of charged neutrino, the tau.Although the third neutrino was definitely identified, there as still very little known about it.
question 1
In lines2-3 the term "not subject to "means________
A. not the topic of
B. not controlled by
C. not aware of
D. not necessary for
I chose A, but the correct answar is B.I don`t know why.
question 2
What was Wolfgang Pauli`s research about?
A. Naming new particles
B. Radiation enery levels
C. Neutrino movement
D. The strong nuclear force.
The correct answer is B.However,I can`t find any cite for article.
question 3
In line 16, the term "conclusively shown" refers to____.
A. atomic particles
B. radioactive decay.
C. the movement of neutrinos.
D. a kind of lepton.