'Impossible' questions that I had to answer

I thought I was doing well in my Arabic language studies. Suddenly, today's lesson asked me to answer the questions shown below. Yes, I learned them before but I never thought that I should have to remember them. Well, I finally answered the questions, as shown. (Of course, I had to look back at my previous notes :)

Questions

1. What is genetive case called?
2. What is a nominal sentence called?
3. What is a preposition called?
4. What is the subject of a nominal sentence called?
5. What is the interrogative article called?
6. What is the second part of a nominal sentence called?

My answers

1. حَالَةُ الْجَرِّ Haalatu al jarri (pronounced as Haalatuljarri)
2. الْجُمْلَةُ الاسْمِيَّةُ aljumlatu lismiyyatu
3. حَرْفُ الْجَرِّ Harfu al jarri (pronounced as Harfuljarri)
4. مُبْتَدَأٌ mubtada'un
5. أَدَاةُ اﻻسْتِفْهَامِ adaatu listifhaami
6. الْخَبَرُ alkhabaru

My comments

1. Look at all the words that begin with article ال. Do you notice that the vowel fathah  َis not written on the huruf alif, ا? As far as I know, the vowel fathah  َis not allowed to be written on the huruf ا. I don't know why.
2. Now look at the words that begin with اﻻ in answers 2 and 5. Do you notice that the vowel kasrah  ِis not written under the huruf lam ل although it is pronounced when speaking? You don't know why? Well, neither do I :)