A、It allowed the once complex language to decay into such a "simple" language. B、Overtime the modern Indo-European languages hav

I: Good morning, listeners. Today, we are very happy to have Doctor Michael Williams to discuss evolution of language. Well, Michael.
M: Thank you. Very pleased to meet you all here.
I: Michael, there have been many theories about why languages change. Can you give us some examples, please?
M: Of course. The first established theory of language change is one of decay and decadence proposed in the 18th century view. Their reasoning is that the old Indo-European languages like Sanskrit, Greek and Latin all have complex declension and conjugation schemes. Overtime the number of cases dropped, and the modern Indo-European languages have far fewer cases for declension and conjugation. It is said that people get increasingly careless about their speech, so they are "decadent" and have allowed the once complex language to decay into such a "simple" language.
I: Sounds interesting.
M: But this "decadence" argument has one major flaw. Even though the number of declensions and conjugations has dwindled, other parts of speech such as particles and auxiliary verbs have evolved to take their place. Anything that can be expressed in the ancient tongue can still be expressed today. Ultimately, this theory is highly subjective, as it relies on personal opinions, not scientific facts, of what is "highly evolved" and what is "decadent". So, strictly speaking, this cannot be called scientific explanation.
I: Right. Is there any other theory?
M: The next theory, proposed by the Neogrammarians, is one of natural process. They stated that changes are automatic and mechanical, and therefore cannot be observed or controlled by the speakers of the language. They found that what to a human ear a single "sound" is actually a collection of very similar sounds. They call it "low-level deviation" from an "idealized form". They argue that language change is simply a slow shift of the "idealized form" by small deviations.
I: Are there any problems concerned with this theory, too?
M: Of course. The obvious problem here is that without some kind of reinforcement, the deviation might go back and forth and cancel out any change. Then the Neogrammarians patched this theory by adding reasons for reinforcing the deviation such as simplification of sounds, or children imperfectly learning the speech of their parents.
I: Simplification of sounds? Can you explain it a little further?
M: Sure. The simplification of sounds basically states that certain sounds are easier to pronounce than others, so the natural tendency of the speakers is to modify the hard-to-say sounds to easier ones. An example would be the English word "nuclear", which many people pronounce as "nucular".
I: But who knows which one is more difficult to pronounce, "nuclear" or "nucular"?
M: Exactly. Different people may give different answers. Simplification no doubt exists, but using it as a reason of language change is too subjective to be scientific. There is another problem with children incorrectly learning the language of their parents. Let’s take an extreme case in the form of immigrants. What is observed is that children of immigrants almost always learn the language of their friends at school regardless of the parents’ dialect or original language. Children of British immigrants in the United States, for example, nearly always speak with one of the many regional American accents. So in this case, the parents’ linguistic contribution becomes less important than the social group the child is in.
I: I agree. Any other theories?
1. Which one is NOT old Indo-European language?
2. What is the main problem with the theory of decay and decadence?
3. Which statement is WRONG according to decay and decadence theory of language?
4. Which can be the best example of simplification of sounds?
5. According to Michael, why do children of immigrants have problems in learning their mother tongue?