English and German have relatively large vowel inventories. What reason does the discussion provide for this?
A、These languages tend to have a simpler syllable structure than other languages, and need more differences between vowels.
B、Earlier distinctions between long and short vowels developed into vowel quality contrasts in these languages.
C、Because of extensive language contact, these languages borrowed vowels from each other.
D、These languages have a long writing tradition, influencing the number of vowels that can be expressed.
E、These languages are relatively old and had more time to develop the vowel inventory.