English and German have relatively large vowel inventories. What reason does the discussion provide for this?
选项：

A:These languages have a long writing tradition, influencing the number of vowels that can be expressed.
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 are relatively old and had more time to develop the vowel inventory.
E:These languages tend to have a simpler syllable structure than other languages, and need more differences between vowels.