does began have a short vowel

No, the word "began" does not have a short vowel. It has a long vowel sound. The "e" in "began" is pronounced as /iː/.

does began have a short u

No, the word "began" does not have a short "u" sound. It has a short "e" sound, pronounced as /ɛ/.

does oxygen have a short u

No, the word "oxygen" does not have a short "u" sound. It has a short "o" sound, pronounced as /ɑ/ or /ɒ/.

does copy have a short u

Yes, the word "copy" does have a short "u" sound. It is pronounced as /ˈkɒpi/.

does very have a short u

No, the word "very" does not have a short "u" sound. It has a short "e" sound, pronounced as /ˈvɛri/.

does until have a short u